‘TEXAS AGRICULTURAL EXPERIMENT STATION

' BULLETIN NO.‘ "180   I OCTOBER, 191s

DIVISION OF ENTOMOLOGY

THE TURNIP LOUSE

 

POSTOFFICE:
College Station, Brazos County, Texas

AUSTINTEXAS
Von Boeckmann-{orllgs C0., Printers
J .

[Blank Page in Original Bulletin]

° A143-1015-10m

‘TEXAS AGRICULTURAL EXPERIMENT STATION

BULLETIN N0. 18o OCTOBER, 191s

DIVISION OF ENTOAIOLOGY

THE TURNIP LOUSE

BY
F. B. PADDOCK, B. S. E.
Entomologist in Charge; State Entomologist.

 

POSTOFFICE:

College Station, Brazos County, Texas

~@»
AUSTIN, TEXAS
VoN BoEcxMANN-llflrgzss ($0.. Pamrnns

AGRICULTURAL AND MECHANICAL COLLEGE OE TEXAS

\V. B. BIzzELL, A. M., D. C. L., President

TEXAS AGRICULTURAL. EXPERIMENT STATION
BOARD OF DIRECTORS

loHN I. GUION, President, Ballinger .................... ..
.. J. HART, Vice President, San Antonio  . ...... ..
:1. H. AsTIN, Bryan ................................................. ..

l‘. E. BATTLE, Marlin ........ 
N. C.

BREIHAN, Bartlett ........................................ ..
'. F. KURENA, Fayetteville ................... f. ............... ..
7V. A. MILLER, JR., Amarillo .................................. ..
8. B. DAVIDSON, Cucro ............................................ ..

................................................. .. Term expires 1919

 ...................... ..Term expires 1919

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............................. .. Term expires 1921

   
  
 
     
  
  

Term expires 1921

MAIN STATION COMMITTEE

L. J. HART, Chairman

J. S. WILLIAMS

\V. A. MILLER, JR.

GOVERNING BOARD, STATE SUBSTATIONS

>. L. DowNs, President, Temple .......................... ..
IHARLEs RQGAN, Vice President, Austin .............. ..
7V. P. IIORBY, Beaumont ........ .. . ................................. ..
'. E. BOOG-SCOTT, Coleman .................................... ..

 
 

.................................................... ..Term expires 1919

....Term expires 1917
....Term expires 1917

 

.................................................... ..Term expires 1921

*STATION STAFF

IDMINISTRATION
B. YOUNGBLOOD, M. S., Director
A. B. CoNNER, B. S., Vice Director
CHAs. A. FELKER, Chief Clerk
A. S. WARE, Secretary

HVISION OF VETERINARY SCIENCE
M. FRANcIs, D. V. S.,‘ Veterinarian in
Charge _ _
H. ScHMInT, D. V. M., Veterinarian
)IVISION OF CHENIISTRY

G. S. FRAPs, Ph. D., Chemist in Charge;
State Chemist _
R. H. RIpoELL, B. S., Assistant Chemist
FRANK HopoEs, B. S., Assistant Chemist
W. T. P. SPRoTT, B. S., Assistant Chemist
JIVISION OF HORTICULTURE
H. NEss, M. S., Horticulturist in Charge
W. S. HoTcHKIss, Horticulturist
“VISION OF ANIMAL HUSBANDRY
J. C. BURNS, B._S.,_Animal Husbandman,
Feeding Investigations.
J. M. JoNEs, M. S., Animal Husbandman,
Breeding Investigations
HVISION OF ENTOMOLOGY _
F. B. PAppocR, B. .  Entomologist in
Charge; State Entomologist _
. K. COURTNEY, B. S., Assistant Ento-
mologist
HVISION OF AGRONOMY
A. B. CONNER, B. S., Agronomist in Charge
A. H. LEIDIGH, B. S., Agronomist
H. H. JoBsoN, B. S., Agronomist _
Louis WERMELsRIRcHEN, B. S., Agronomist
“VISION OF PLANT PATHOLOGY AND
PHYSIOLOGY
F. H. BLODGETT, P_h. D., Plant Pathologist
and Physiologist in Charge
N. D. ZUBER, B. S., Fellow.
*DIVISION OF FARM MANAGEMENT
' REX E. WILLARD, M. S., Farm Management
Expert in Charge
DIVISION OF POULTRY HUSBANDRY
R. E. HARvEY, B. S., Poultryman in Charge
DIVISION OF FORESTRY

J. H. FosTER, M. F., Forester in Charge;
State Forester

DIVISION OF FEED CONTROL SERVICE

JAiviEs SULLIVAN, Executive Secretary
CHAs. A. FELKER, Chief Clerk

J. H. RoGERs, Inspector

. H. W000, Inspector

. H. WoLTERs, Inspector

. D. PEARcE, Inspector

. M. WIcREs, Inspector

T. B. REEsE, Inspector

SUBSTATION NO. 1: Beeville, Bee County
E. E. BINFORD, B. S., Superintendent

SUBSTATION NO. 2: Troup, Smith County
W. S. HOTCHKISS, Superintendent

SUBSTATION NO. 3:
County
N. E. VVINTERS, B. S., Superintendent

SUBSTATION NO. 4: Beaumont, Jeiferson
County

H. H. LAUpE, B. S., Superintendent

SUBSTATION NO. 5: Temple, Bell County
A. K. SHORT, B. S., Superintenderft
SUBSTATION NO. 6:
County
T. W. BUELL, B. S., Superintendent

SUBSTATION NO. 7: Spur, Dickens County
R. E. DICKSON, B. S., Superintendent

SUBSTATION NO. 8: Lubbock, Lubbock
County

V. L. CORY, B. S., Superintendent

SUBSTATION NO. 9: Pecos, Reeves County
J. W. JACKSON, B. S., Superintendent
SUBSTATION N0. l0: (Feeding and Breed-
ing Substation) College Station, Brazos
County
T. M. REppELL, Superintendent
SUBSTATION NO. ll: Nacogdoches, Nacog-
doches County
G. T. McNEss, Superintendent _
D. T. KILLOUGH, B. S., Scientific Assistant
“SUBSTATION N0. 12: Chillicothe, Harde-
man County
R. W. EDWARDS, B. S., Superintendent

seas

Angleton, Brazoria

Denton, Denton

CLERICAL ASSISTANTS

TATION

J. M. ScHAEpEL, Stenographer

W. F. CHRISTIAN, Stenographer
ELIZABETH WALKER, Stenographer
J. L. COTTINGHAM, Stenographer
C. L. DuRsT, Mailing Clerk

*As of October 1, 1915

FEED CONTROL SERVICE

DAIsv LEE, Registration Clerk
E. E. KILBURN, Stenogra her
WILLIE JOHNSON, Tag C erk

**In Cooperation withithe United States Department of Agriculture.

................................ ..Term expires 1921 .

CONTENTS.
PAGE
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7

Historical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8

Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._ 8

Food Plants . . . . . . . . . . . . . . . . Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Feeding Habits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9

Viviparous Development . . . . . . . . . . . . _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Seasonal History“ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12

_ 1913-1914 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . . . . .. 12

1914-1915 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14

Hibernation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16

Life History . . . . . . . . . . . . . . . . . . . . j . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Alternate Host Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17

Rearing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24

Description of Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24

Wingless Viviparous Female . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24

Pupa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25

Winged Viviparous Female . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26

Moulting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3s

Number of Generations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37

Age at Which Females Reproduce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 38

Reproductive Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. e38

Longevity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41

Average Number of Young Daily . . . . . . . . . . . . . . . . . . . . . . . . . . .._ . . . . . . . . .. 41

Rate of Increase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41

Effect of Temperature on Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 47

Summer Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 47

Other Species Found . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 47

Natural Enemies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49

Parasites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49

Diaeretus rapae Curt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49

Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49

Life History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 49

Lysiph/lebus itestaceipes Cress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 53

Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 53

Life History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54

Predaceous Enemies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54

Lady Beetles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 55

Syrphid Flies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 58

Lace-Wing Flies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59

Fungous Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59

4: CONTENTS.
PAGE
Artificial Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 62

Season 1913 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 62

Spraying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 63

Turnips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 63

Black Leaf-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 63

Kerosene Emulsion j . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 63

N0. 6 Soap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 64

Cabbage . . . . . . . . . . . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Black Le.1f-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65

No. 6 Soap . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . . . . .. 65

Fumigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 65

Radishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 . . . . . 66

Turnips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67

Mustard . . . . . . . . . . . . . . . . . . . . . . . . .- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Season 1914 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 67

Spraying . . . . . . . . . . . . . . . . . . '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Radishes . . . . . . . . . . . . . .; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 68

Black Leaf-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 68

Sulfur . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Lime Sulfur Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~. 69

Soluble Sulfur Compound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 69

Laundry Soap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 69

Fish Oil ‘Emulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70

N0. 3 Soap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70

Whale Oil Soap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70

Mustard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 70

Turnips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 . . . . . . . . . . . . . . . . . . . . . 70

General Remarks on Plat I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 71

Preventive Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 72

Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 72

Planting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 72

Trap Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . .. 73

Destruction of First Colonies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 73

Clean Culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 73

Spraying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . 74

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 74

Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 75

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

II.

III.‘

IV.

°°9° NPWPP-‘P

10.

ILLUSTRATIONS.
PLATES.

Turnip lice feeding in the flower head of mustard. .9 . . . . . . . . . . . . . . . ..
Above, shelter in which the cage experiments were conducted with the
turnip louse; below, an infested garden, showing radishes which
were killed by a severe infestation of the turnip louse . . . . . . . . . . . ..
Above, empty skins of parasitized lice on cabbage from which the para-

sites have emerged; below, larva and adult of Chrysopa or Lace-wing

"fly, a predlaceous enemy of the turnip louse . . . . . . . . . . . . . . . . . . . ..,
A bucket spray pump properly equipped for spraying against the
turnip louse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Above, a barrel spray pump, with cart, showing one lead of hose -and
attachments for spraying against the turnip louse; below, a hand-
power pump, with barrel supply tank, showing proper attachments

for spraying against the turnip louse . . . . . . . . . . . . . . . . . . . . . . . . . . ..
TEXT FIGURES.

Map of Texas, showing distribution of the turnip louse ‘as determined
up to January, 1915 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

The turnip louse, Wingless viviparous“ female . . . . . . . . . . . . . . . . . . . . . . ..

The turnip louse, winged viviparous female . . . . . . . . . . . . . . . . . . . . . . . ..

Succession of generations in the turnip louse, 1914 . . . . . . . . . . . . . . . . ..

Succession of generations in the turnip louse, 1914-1915 . . . . . . . . . . . . ..

Lysiphlebus testaceipes Cress, a parasite of the turnip louse . . . . . . . . ..
Lysiphlebus testdceipes Cress, ovipositing in the body of a “green

bug” . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The convergent lady-beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
The spotted lady-beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .' . . . . . . . . .

Syrphus americanus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

25

54

68

9 .

25
26
36
37
53

54
56
57
58

II.
III.
IV.
V.
VI.
VII.

TABLES.‘

Generation Series, 1914 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19

Generation Series, 1914-1915 . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . . . . .. 27

Moults of Wingless-Lice . . . . . . . . . . . . . .  . . . . . . . . . . . . . . . . . . .  36

Moults of Winged Lice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 36

Line of Generations, 1914 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39

Line of Generations, 1914-1915 . . . . . . . . . . . . . . . . .  . . . . .  . . . . . . . . .. 40

Reproduction in Winged and Wingless Lice . . . . .  . . . f . . . . . . . . . . . . . . 42

THE TURNlP LOUSE.

BY F. B. PixnnooK, B. S. E., ENTOMOLOGIST IX CHARGE;
STATE ENTOMOLOGIST.

INTYQODUCTPIOX.

For several years complaints have been made of a plant-louse de-
stroying the fall crop of turnips in various sections of the State. It
became evident from the increased number of these letters that the in-
sect was spreading, and that it was a. serious menace to several truck
crops during the Winter. In the early fall of 1913 it was decided to
undertake some investigations of this plant-louse, as it was causing
widespread injury to turnips and related plants. When the ' rk was
started, it was supposed that this insect; was the cabbage louse, Aphis
brasusicae. and that its habits and life history as observed in the South
would probably yiarv considerably from the observations which had
been made upon it in the North. Statements made in the literature
up» to this time were to the effect that in the South during the winter
the cabbage louse was a serious pest of turnips grown as a winter truck
cro .-

ellftei" some preliminary observations, it was deemed advisable to con-
sult descriptions of A. Zirassiicae, in order that all the described forms
might be recogniyed when met with. It was soon evident that the
species which was being taken upon the plants about College Station
did not coincide with the descriptions of A. brass-icae. Material col-
lected from turnips xvas sent to Prof. C. P. Gillette, of Fort Collins,
Colorado, for his determination. His reply was that the specimens
sent were evidently a species xvhich had recently been described in
manuscript by Mr. J. J. Davis, of Latayette, Indiana, as Apihis pseudo-
brassiciae. Material was then sent to Mr. l)avis, and his identification
confirmed that made bv Professor Gillette. As soon as it was evident
that the species which was being investigated was not the cabbage louse,
we took the liberty of calling it the “turnip louse,” as this would more
clearly identify it for the truck grower.

During the tall of 1913 material was collected from turnips at
Iredell, Wortliam, Valley View, Ile Kalb. Daingerfield, Cooledge, Mc-
Kinney and Hitchcock, '.l‘exas. Specimens collected at these places
proved to be A. yrsetrdobrassicae rather than A. brass-abate. It was then
evident that the turnip louse rather than the cabbage louse, was doing
much’ of the injury to the winter turnip crop. It was thought that
further study might show this louse to be generally distributed over the
State. freliminary observations were made during the fall of 1913
upon the habits 0t the turnip louse, and some work was condu.cted
with practical control measures.

In January of 1914 cage experiments were started to ascertain some
of the details of the life history and number of generations of the louse.
The work was continued until August, 1914, at which time the lice
died out in the cages. The work was resumed in September, 1914,

8 TEXAS AGRICULTURAL EXPERIMENT STATION.

and continued for one year. During the fall of 1914 control measures

were undertaken on a much larger scale than in the previous season. ~

Studies on the distribution of the species were also continued. Re-
ports were received from all sections of the State, and these indicated
that the turnip louse was present, and in every case it was considered
a serious pest. Trips have been made to both the northern and south-
ern limits of its range in Texas and considerable time has been devoted
to a study of the varying life history at and between these points.
The turnip louse is now known to be a serious pest in the winter
truck regions of the State. The injury is perhaps most noticeable
upon turnips, though the louse attacks most any of the plants of the
family Cruciferae, especially cabbage and mustard. Not only is this
insect a serious pest in the winter truck regions, but the home gardens
everywhere are often entirely destroyed. It is not possible to estimate
the loss caused by the presence of this insect, but the total sum must
be very large indeed. Often the home gardens are planted twice and
truck growers often lose an entire planting; a big loss when competi-

tion is keen for early crops. In some of the sections the truck growers

will be forced to abandon the growing of crops attacked by the turnip
louse, unless it is brought under control.

HISTORICAL.

In his description of this species,* Mr. Davis says the first specimens
were sent him from Geneva, New York, taken from cabbage in July,
1912. Later in the same year Mr. Davis received specimens on kale
and mustard from Evansville, Indiana. During the fall of 1913, he
also reported the species abundant upon radishes and turnips at
Lafayette, Indiana.

DISTRIBUTION.

It will probably be found after more observations have been made
upon this species‘ that it is generally distributed over the United States,
especially where A. brassicae is found, as A. pseudobrassicae feeds upon
many of the same plants, especially the cultivated species. In the
past the later species of plant louse has probably been mistaken for the
former in many instances. The turnip louse has already been reported
from New York (Schoene), Indiana (Davis), Minnesota (Maxson),
Oklahoma (Sanborn), Louisiana (Tucker), Florida (Mason), and
Texas, Reports received from all the Southern States, Georgia ex-
cepted, indicate the presence of this species, though examination of
material from various localities should be made to avoid the confusion
of this ’Form with the cabbage louse. '

Reference to the accompanying map will give an idea of the distri-
bution of the turnip louse in Texas, as determined up to January,
1915. We now have received 89 reports from '76 towns located in
6O counties, showing the presence of the louse. The general distribu-
tion is probably well confinedto the more humid sections of the State.
At present the species is found between the 26th and 34th parallels of
latitude.

*Canadian Entomologist, XLVI, 7, p. 231.

THE TURNIIf LOUSE. ,9

FOOD PLANTS.

Aphis pseudobrassicae has been taken upon turnip, radish, cabbage,
cauliflower, mustard, kale, rutabaga, lettuce and bean in. our Work at
College Station. In addition to these plants this species has been re-
ported from sections of “fexas upon rape, kale, kohl-rabi and collard.

Mr. A. C. Maxson, of Longmont, Colorado, sent us specimens of this
louse Which had been taken on rutabaga "at St. Cloud, Minnesota. Mr.

Davis described the species from specimens taken on radishes, turnips ,

and rape at Lafayette, Indiana. He also records the receipt of speci-

Fig. 1.—Map of Texas, showing distribution of the Turnip Louse as determined up to
January, 1915 (Original).

mens from Mr. J . W. Schoene at Geneva, New York, taken from cab-
bage with the note that they likewise occur on kale and mustard. Mr.
A. C. Mason has sent us specimens of this species taken on cabbage at
Gainesville, Florida.

FEEDING HABITS.

This louse feeds for the most part upon the tender leaves of the host
plants, and usually upon the under sides. In the case of turnips the
infestation starts upon the leaves of medium size, though these leaves
often become quite large by the time the infestation is severe. When

1O TEXAS AGRICULTURAL EXPERIMENT STATION.

this stage is reached the under sides of the leaves are almost entirely
covered with the masses of lice. The more tender leaves nea.r the
center of the crown are sought by the young ones when the large leaves
become crowded. When the infestation is very heavy these central
leaves are crowded on both sides with the lice. Under normal condi-
tions the lice do not move about much; if the infestation is not heavy
the young ones establish themselves very close to the parent. In fact,
the female is often forced to swing the rear end of her body around
in order that room may be found for additional young. If the leaves
are crowded the young lice are active for a time in search of a good
feeding place, but under normal conditions they do not move from the
place Where they first become established. Urjion heavily infested leaves
the moulted skins of the lice are found on top of the masses.

It is doubtful if the young lice can travel very far over the ground,
especially; the soils which are coarse and loose. ’l‘hey' may go from
plant to plant when the leaves are touching, but even such migration is
unusual. When a. single leaf becomes croyvded pupae are developed
and the winged lice fly to other plants. Only once has a migration of
Wingless lice been observed. During the late fall of 1913, in the horti-
cultural gar-den of the College the infestation upon the turnips was
very heavy. On one side of the patch was fallow ground for fully 15
feet and next to this was a patch of turnips sown broadcast. These
turnips were small, for the most part, having only four leaves, and the
plants were scattering. “llhese Wingless lice, fron1 half-grown to adults,
were going in hordes from the old turnips across the fallow ground,
which was dry and quite well pulverized, to the young turnips. The
rate of travel of the lice Was very rapid, and they traveled in nearly a.
straight line from the old turnips to the new plants. The young tur-
nips Were soon covered with lice, and Within twenty-four hours all the
plants were killed. .

In the early spring of 1914 old turnips which had been left in the
field over winter sent. up seed stalks and floyvered. The lice which were
feeding upon the leaves near the crowns of these plants moved up the
stalk as it grew, feeding upon the under sides of the young leaves near
the aXils. When the flowers developed the lice clustered in the heads,
at the bases of the stems of the florets. Here viviparous reproduction
continued until the seed pods became hard and dry. It was evident
that the winged lice selected these high flower stalks to start the new
infestation. Winged lice were frequently observed which had just
alighted from the flowers or had but recently gone in among the stems
0f the florets and given birth to one or two yroung. Throughout the
spring the feeding of the lice upon the turnips was confined to the
flower or seed stalks. When the seed pods were first formed the lice
fed upon the stem, or in case of l1ea.v_v infestation, up-on the pod itself.
When the seed pods became hard and the stalks dry, the lice left the
turnips, possibly in search of some alternative host.

During the winter the lice migrate from the outer portions of the
plants and mass upon the small leaves at the center of the crown. Here
they prefer to feed upon the under sides of the leaves. They also may
be found upon the upper sides of the bases of the smallest leaves. This
change in place of feeding is for protection from the winter weather, as

Plate I—'I‘urnip lice feeding in the flower head of mustard. (OriginaL)

THE TURXIP LoUsE. 11

the lice are thus protected from snoW and rain, from Wind and to some
extent from cold temperatures. After a. very hard freeze in the Winter
the lice become active in the search of leaves Which may be in good
condition for food.

Upon radishes the feeding habits of the lice are much the same as
upon turnips. Apparently the infestation can become heavier upon
single radish plants than up-on turnips before pupae are developed and
the Winged lice fly to ncW plants. In the spring and early summer the
lice may be found feeding in the floWer heads of this plant in the same
manner as they feed upon the flovvers of turnips. Aslate as May 18,
1915, the lice Were found on the flowers of some isolated radishes.
Young radishes in the same garden Were but lightly infested at that
time. During the tWo seasons in Which observations have been made
in one garden, the radishes and turnips Were soWn side by side. Both
years the infestation in the garden started upon the radishes, and even
spread for a time on this plant before starting upon the turnips. The
radish plants are easily killed by a severe infestation.

Upon mustard the lice are found mostly in the deep curls of the
smaller leaves, but they do not attack this plant as readily as they do
the radishes and turnips. During the fall of 1913 the radishes and
‘turnips Were dying before the mustard in the same garden Was attacked,
and during the fall of 1914. the lice left the mustard to go to the
radishes and turnips i11 the same garden. During the Winter of 1914
lice Were observed upon mustard plants Which had gone to seed. Here
the lice Were feeding in the stems of the florets exactly as they had
been upon the turnips in the spring. The lice attacking mustard at
this time Were entirely in the floWer head. Both the Winged and Wing-
less forms Were observed feeding in this manner upon the mustard.

When feeding upon cabbage the lice may be found upon the under
sides of some of the outer leaves. This is especially’ true When the in-
festation is started on young plants. If the plants are of much size,
as they often are, thcvvingerl females go to the smaller leaves near the
inside of the head. Here the lice may be found upon the upper sides
of the leaves also, but usually upon the under sides. The lice are found
mostly along the larger veins of the leaves, especially When the infesta-
tion is just starting. During the Winter those lice Which live over
upon cabbage are found very close to the base of the leaf and upon
those leaves just outside of the head. Very closeinspection is neces-
sary to detect the lice upon this plant during the Winter.

In the case of cauliflower the lice have been observed: only upon small
plants, and the feeding habits here Were the same as upon cabbage.

Upon lettuce the lice Were found feeding upon the tender leaves of a
head variety in much the same manner as upon cabbage.

When feeding upon beans the lice Were entirely upon the under sides
of the leaves, near the bases.

Often an infestation in a. garden Will start from one spot and spread
from this in all directions. Where such an infestation starts the plants
are usually killed before most of the garden is even infested. A garden
may be infested in several places at ‘once, and the infestation from each
source Will spread until meeting that from other sources.

l2 TEXAS AGRICULTURAL EXPERIMENT STATION.

VIVIPAROUS DEVELOPMENT.

In Texas the normal form of reproduction in the turnip louse is
asexual throughout the entire year. N0 sexes have so far been ob-
served either in the breeding cages or the fields. It seems that each
generation is made up entirely of viviparous females. Webster* states
that south of the 35th parallel the sexual forms of plant-lice have been
observed but rarely, except at high altitudes. The farthest north in
Texas that observations have been made upon A. pseudobrassicae is
Wichita Falls, just south of the 34th parallel. It is evident that at
this point sexes do not occur and the viviparous females survive the
winters.

Mr. Davis in his (briginal paper (l.c.) says‘: “The sexes have not
been found, and our present knowledge leads us to believe that the
more usual means of passing‘ the winter is as viviparous females.” Re-
cently Mr. Davis wrote that their searches had not revealed the sex
forms‘ at Lafayette, Indiana.

SEASONAL HISTORY.

Most of the field observations on the turnip louse have been made

at College Station, though some time has been spent in the two ex-

treme sections of the State, Brownsville in the south and Wichita Falls
in the‘ north. The field notes made on the turnip louse during two
seasons at College Station are briefly reviewed here.

1913-1914.

As the Work of this season was not organized early, the first observa- '

tions Were not made until October 9. At that time the turnips in
this vicinity were very heavily infested with the louse, though the ex-
treme infestation had not existed long enough to induce the formation
of xvinged lice. However, within a. week afterwards fully 50 per cent.
of the lice found upon turnips were winged females. In another week
fully '75 per cent. of the lice were winged and the pupae were abundant.
The very large proportion of winged females at this time resulted later
in an extensive infestation of the host plants in this vicinity.

About the time of the heavy infestation and production of winged lice
on the turnips, the radishes in the College garden became infested. The
winged lice migrated from the crowded turnips to the radishes in the
same field. At the end of two weeks these radish plants were heavily
infested, at which time only 1 p-er cent. of the lice present were winged
but fully 25 per cent. were pupae. This tendency to the formation of
winged lice was to be expected. as the radishes and turnip-s in the
garden had suffered severely from the extreme infestation. Within a.
month after the first appearance of the lice upon the radishes the winged
lice were leaving the plants. During that month, however, the radishes
were almost killed bv the extreme infestation.

It was not until November 1, 1913, that the turnip louse was first
observed upon cabbage in this vicinity. three weeks after the maximum

*Bureau of Entomology, Bulletin N0. 110, p. 47.

THE TURNIP LoUsE. 13

infestation, upon turnips. This infestation on the cabbage started so
late tha.t the low temperatures at that time materially retarded the rate
of reproduction. For some time the lice increased slowly upon the
cabbage, but xvithin three weeks from the time they were first observed
there was a decided migration from the cabbage to some other host
plant. By the middle of November, when the infestation was slight,
fully 50 per cent. of the lice were winged. From that time on the lice
gradually disappeared from the cabbage.

Early in November the lice were very abundant upon mustard in the
same garden where the radishes and turnips had been so heavily in-
fested. In two weeks after the lice were first observed upon the
mustard the infestation there was much more severe than upon the
other host plants in the garden. While the mustard suffered some from
the presence of the lice it did not show the effects of the infestation
to the extent that the radishes and turnips did. Perhaps this was due
to the fact that the lice migrated back to the radishes and turnips after
those plants had recovered from the previous attack.

In the College garden, well along in the season, the lice were very
abundant upon turnips, radishes and mustard. As all of these plants
began to suffer from the severe. infestation, there was need for new
food. Beans which were planted between mustard and radishes were
found to be infested with the turnip louse on November 21. The
colonies of lice at that time were scattered upon the under sides of the
leaves. The infestation did not persist long, due to natural control fac-
tors, but it is doubtful if the lice could continue long upon this host.
The infestation upon this host was very light, consisting of scattered
individuals, both winged and Wingless lice, with no well-defined colonies.

Upon the turnips in the College garden the lice continued to increase
to such an extent that unsprayed plants were dead by November 21,
at which time the lice were found upon most every variety of plant
then in the garden. Fully 3O per cent. of the-lice on the infested

 

plants were winged females and 50 per cent. were pupae, so that a-

general migration took place which infested the sprayed plants.

' During the last week of November and the first week of December
very heavy rains occurred which apparently killed every louse upon all
the plants in this vicinity. From December 19, 1913, ‘to March 5,
1914, no lice were found on any plant in the fields. From December
20, 1913, lice were kept in breeding cages out doors for general ob-
servation purposes. From this date through January and February all
study of the lice was made in these cages. The reproduction during
these months was quite constant though governed strictly by the tem-
peratures, since the lice reacted quickly to a change in temperature.
On February 6, 1914, a sudden drop in temperature to 1'7 degrees F.
occurred, but hardly 5 per cent. of the lice succumbed, these being the
old females. Winged lice emerged in great numbers in the cages dur-
ing the latter part of February, at which time it was quite cool. The
host plants in the cages became heavily infested by Ma.rch 1, and
the lice were purposely allowed to fly from them to infest the experi-

_ mental fields.

From the cages the lice infested the turnips in the immediate vicin-
ity only, the migration seeming to be very limited. This migration

14 Texas AGRICULTURAL EXPERIMENT STATION.

from the cages continued throughout March and April. The plants
which were first infested close to the cages never suffered, as the lice
seemed to remain upon them but a couple of Weeks and then the re-
sulting Winged lice migrated to other plants. During the latter part
of April the Winged. lice Were particularly active in the air during the
Warm afternoons. Some turnips in an adjoining field Which had gone
to seed seemed to attract many lice. Throughout April there was a
general migration of the lice from the turnips in the cages and from
the plants in the fields. During this time the infestation was never
heavy upon the turnips and there was a continuous production of
Winged lice. The small colonies upon the turnips continued to grow
smaller all the time, as a. portion of each brood developed into pupae
and later to winged lice. By l\l.ay 1 there were- but few lice upon
the turnips in the field, though it was possible to find lice as late as
June 6. By this time the turnips ceased to grow well on account of

the heat and (lrouth.
1914-1915.

The lice were first observed upon turnips in the College garden on
September 10, at which tiime the infestation had just started. The
infestation consisted almost entirely of Wingless lice at the head of Well
formed colonies. On this date the lice Were also found upon the
radishes and mustard which were growing on either side of the turnips.
The infestation in this garden started upon the radishes near the West
end. The spread of the lice Was from west to east, but this was evi-
dently not due to the Wind, as at that season the prevailing Winds Were
from the south. -

Within a Week after the lice were first observed upon the turnips,
the plants Were heavily infested and a few winged lice Were found, Well
scattered over the field. At this time pupae Were developing, though
not alWa_vs in theplaces of heaviest infestation. Development of pupae
at this time, When dissemination is general and rapid, appears to be
normal. At other seasons of the year pupae develop only under the
stimulus of excessive infestation. The radish plants seem to shoW the
effects of severe infestation more readilv than the turnips or mustard.
When the general spread of the lice started the leaves of the radishes
were larger than those of the other plants. and it may have been that
the lice were attracted to them. At no time Were the lice as bundant
upon mustard as upon the turnips and radishes.

The infestation increased rapidly upon the radishes and turnips, and
to such an extent that by the end of the second Week the leaves of
those plants were entirely covered with the lice. At that time fullv
'75 p-encent. of the lice present Were pupae and 10 per cent. Were
Winged lice and, as a result, other fields in the vicinity Were becoming
infested. Some of the gardens Were seemingly Well isolated from anv
infested host, but the lice became well established upon all. As the
radishes and turnips began to die, the lice became more plentiful upon
the mustard, though the latter Was evidently not as desirable a food as
the other plants.

The very vigorous spraying conducted in the College garden doubt-
less altered the seasonal development of the louse at that time. The

THE TURNIP Lo USE. 15

pest was held in check after October 1, but there was a marked
tendency toward the formation of ivinged lice only. At one time fullv
90 per cent. of the lice present on the plants were pupae. On Xoveni-
ber 1, there were but few winged. females present and but few wing-
less; though these were of all ages. At this time also a few Winged
lie-e were first observed upon cabbage, but this infestation was not last-
ing‘. Contrary to expectations, no lice could be found upon the cab-
bage during the winter.

The lice were present on the radishes and turnips in the gardens in
this vicinity throughout the entire winter. There were no severe tem-
peratures during the winter, so the infestation steadily increased. In

-Februarv this species, was present in sufficient numbers to result in a

usual infestation of spring crops.

During the first part of Blarch the infestation of lice on turnips was
very light. This consisted of apterous individuals well scattered over
the field. The feeding at this time was confined entirely to the flower
heads of the fall turnips... During the latter part of April the lice be-
gan migrating‘ from the flower stalks, though the winged females were
never present in large numbers. The lice ap-peared on the spring plant-
ing- of turnips in earl)‘ hfay. This infestation consisted of large, well-
defined colonies, ivhich were found over the entire field. The lice never
became abundant on these turnips. “There never was a heavy produc—
tion of winged females, but the lice entirely disappeared from the fields
by the middle of June.

On l\Iarc-l1 1 the lice were quite abundant on the winter radishes
in the gardens. By March 15, 75 per cent. of all the lice in the
gardens were found on radishes. The infestation consisted of 50 per
cent. of apterous lice of all ages, 30 per cent. pupae and 20 per cent.
winged. females. A few (lays later only apterous lice were found on the
radishes. The feeding of the lice during this season was entirely in
the flower heads of the plants. The spring planting of radishes was
not infested with lice until April 6. This infestation was light and

consisted mostly of apterous lice in small colonies. The lice increased

on the radishes until April '20. and then the number decreased for a
time. A light infestation of lice persisted on young radishes in the
gardens throughout lvfay. During the latter part of this month there
“'38 a continued production of pupae, though these were never abund-
ant upon the plants. The winged females were seldom observed. The
lice gradually disappeared from the plants, and by the middle of June
no lice IVQTQ observed in the gardens. '

By the middle of March the lice were quite abundant upon mustard
plants. This infestation consisted mostly of apterous lice, which were
feeding on the leaves near the ground. These lice migrated to the
flower heads about April 1. Though the infestation at this time was
apparently of apterous lice, the spring mustard became infested during
the first of April. During the first half of April the infestation on
the old mustard increased heavily, and the lice moved from the flower
heads to the young leaves near the top- of the plants. A few pupae
were observed at this time, but winged females were seldom seen. Dur-
ing the first part of May the infestation increased on the spring mustard.

16 TEXAs AGRICULTURAL EXPERIMENT STATION.

About the middle of the month pupae developed, and gradually the lice
disappeared from this plant.

During the last half of April there was a light infestation of lice
on rutabagaeturnips. These were planted in the same garden as the
turnips, radishes and mustard, which has been discussed above. About
the same time lice were found on kale in the same garden. This in-
festation consisted of immature apterous lice.

On June 1 a rape field tvas found heavily infested with lice. Fully
8O per cent. of the lice were pupae which were about ready to emerge
aswinged females. But few winged females were observed on the
plants at this time. The apterous females were surrounded by small
colonies of young. This heavy infestation practically killed the rape.

' HIBERNATION.

From the foregoing observations made at College Station it is evi-
dent that the turnip louse continues to breed throughout the winter.
Seldom is the temperature low enough to prevent reproduction, though
the daily number of offspring is very low most of the time. There are
a few days during the winter at College Station when the lice, especi-
ally the older females, do not reproduce. The temperatures below
which the lice are not active are indicated in our cage records, which
are shown in Table I.

Trips were made to Wichita Falls, the most northern Texas point
known to be infested, and observations made on the winter conditions.
Here the licc pass the winter upon turnips and mustard; seldom on
radishes. The winter temperatures are sometimes quite low, 15 to 20
degrees F., and it is not uncommon to have snow. For much of the
time during the winter the reproduction is indeed very slow, and there
are many days at a. time when the temperature is not above 32 de-
grees F. During such periods the lice do not reproduce, and in this
we have the nearest approach to hibernation that occurs in the State.
During the last of January, 191-5, observations were made at Wichita
Falls after a long cold spell. Apparently only a few lice had been
killed b'_v the cold and. snow, and most of these were old females, still
upon the leaves.

At Brownsville, the southernmost point visited, winter conditions are
vastly different from those found at College Station or Wichita Falls.
At Brownsville the conditions in January are very similar to those pre-
vailing at College Station in October. The daily reproduction in the
fields near Brownsville in January was four to six young, and in pro-
tected places it was as high as eight.

LIFE HISTORY.

The life history of A. pseudobrassicaie in the various sections of the
State is a perplexing problem. Although the louse is a pest in all parts
of the State during the fall and early winter, we have been unable to
determine where or how it passes the remainder of the year. In the
fall the lice make their first appearance on the turnips about the time
they develop four leaves. At Waco the lice are first noticed upon the
turnips in August and are present continuously on turnips and radishes

THE TURNIP Lousn. 17

until the following May. At College Station the lice do not make their
appearance until September 1. The turnips and radishes are then
attacked by the louse during the winter and until May of the next year.
Further south, at Beaumont, Galveston and Beeville, the lice appear
upon the turnips between September 15 and _October 1. At Browns-
vills the turnip crop is not up until about November 1, but the lice

are found on mustard as early as August 1 and continue to infest’

this crop until the turnips are available. The turnip crop experiences
the heaviest damage during November. By December most of the tur-
nips have been either destroyed by the pest or harvested. Throughout
the winter the lice feed upon radishes and mustard a.nd on what tur-
nips remain in the ground. In the spring the infestation extends to
the new crops of turnips, radishes, etc., and increases in severity. At
Brownsville, after May 1, practically all eruciferous crops, except
mustard, are over with.

At Wichita Falls turnips are not available for the lice until about
September 1, a.t which time the first infestation is observed. Were
the turnips soxvn as early at Wichita Falls, or other northern points,
as they are at Waco, the lice would probably appear on them as early as
at the latter place. The time of appearance in fall seems to depend
upon the availability of turnips for food. At Wichita Falls the winter
is passed upon turnips and mustard, and in the spring the infestation
extends also to radishes, continuing until July.

ALTERNZATE HOST PLANTS.

A review of the life histories here given show that there is a portion
of the year during; which the louse is not found upon any cultivated
host plant. At College Station the lice begin to migrate from the cul-
tivated plants with the approach of hot. dry weather, during April.
Tllhroughout this month there is a decided. tendency to the Production
of winged lice, even when the food supply is good. During this time
the number of xvingless lice gradually decreases and the infestation
finally dies out. There are never very many winged lice present dur-
ing May, as the reproduction seems to be much retarded. These winged
females, while the migration is. in progress, are not different in struc-
ture from those taken during the fall and winter. Also the first winged
lice taken in the fall upon turnips are in no respect different. from
those found later.

With the approach of hot, drv weather there is a. decide-d reduction
in the number of young produced daily and all of the stages of the life
history are lengthened, much the same as under winter conditions. It
is quite evident that the summer conditions are even more trying than
the winter. At College Station there are normally four months of the
_year when the turnip louse is not found upon cultivated plants. How-
ever, some of the host plants, such as mustard and radishes, are some-
times in the garden during the entire summer.

At Brownsville the radishes and turnips are in the ground from Oc- _

tober 1 until the following May hlustard is grown until June, and
may be found in small patches during the entire summer. The earlv
fall crop of mustard is available in August, but the lice do not become
abundant on it until a month later. There .is a period of four, and

18 TEXAS AGRICULTURAL EXPERIMENT STATION.

perhaps five, months during the year when the turnip louse is not found
upon the cultivated host plants. At Wichita Falls there is only one
month—-July-—cluring which there are none of the cultivated host
plants in the gardens. However, the lice are not found upon these
plants from May until September, during which time the lice must ex-
ist upon some other host plant.

19

THE TURNIP LOUSE.

 

 

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20 TEXAS AGRICULTURAL EXPERIMENT STATION.

 

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ioucflnonvlm m-AQAJH

21

THE TURNIP LOUSE.

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22 TEXAS AGRICULTURAL EXPERIMENT STATION.

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110118191199 

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24 Texas AGRICULTURAL EXPERIMENT STATIoN.

BEARING METHODS.

The rearing work, when not otherwise stated, was conducted under
as nearly normal conditions as was possible in outdoor cages. Turnips
were used for the host plants in all the cage experiments; plants of
some size were transplanted from the field to large flower pots. These
plants were so trimmed that only three or four small leaves remained
and as the new leaves became established the old ones were cut off, one
at a time. With this reduced leaf area, it was possible to study the
habits of the lice carefully, and it was not difficult to lo-cate the old
and young lice. The turnips were kept in the best possible growing
condition and a single plant was never used for more than a single gen-
eration. The turnips were transplanted some time before they were

to be used, in order that they would be well established in the pots.’

Large lantern globes xvere used to cover the plants, and on top of these
white lawn was drawn tightly. The pots were placed on a stand in
the open and this stand was so arranged that thE plants could be pro-
tected in times of severe wind and storms. In May, 1915, a cage
shelter was constructed along lines suggested by Mr. J. J. Davis of the
Bureau of Entomology.

On June 23, 1915, all lice were transferred to radishes for host‘
plants. The turnips could not be grown well at this time of the year
and the lice could not be kept under proper conditions. ‘Observations-
and some preliminary tests showed that the lice even prefer radishes at
this season. ‘

The generation series were started in January, 1914, and continued‘
until August, 191-1. From June 1.0 until August 6 the work was"
conducted by W. W. Marshall, then Assistant Entomologist?‘ in this-
Division. His services are here acknowledged. The series was started
again in September, 1.91.4, and conducted throughout one year. The
first-born of each generation was transferred to a new host, and all
other young produced by each female were counted and taken from the
plant. The lice were handled with a very small sable hair brush, which
did not seem to injure them in any way. When once a generation was"-
established upon a plant the lice were moved as little as possible through-
out their life cycle. While removing the young lice the adults were dis-
turbed only when necessary, so they often remained in the same posi»
tion for days at a time.

DESO RIPTION OF FORMS.

The following descriptions of the forms of this louse taken in our"
work are the original ones made by Mr. J. J. Davis, which appeared
in the Canadian Entomologist, Vol. XLVI, No. 7, p. 232:

Wingless Viviparons Female.

Entire body pale whitish green, head slightly dusky. Abdomen with a longi-A
tudinal row of impressed dots along each side in a, line with the cornicles; also
on each side of the median dorsal line is a row of transverse shining areas with
a reticulated surface, those on the last four or five segments usually united;
and a similar row of smaller areas on each side. These shining reticulated

areas contrast with the rest of the body, which is dull and very slightly pul-'

_Plate II. Above, shelter in which the page experiments were conducted with the tur-
,_n1p lou_se; below, an infested garden,_showing radishes which were killed by a severe
infestation of the turnip louse. (OriglnaL)

25

verulent. Thoracic segments with similar transverse areas. In specimens just
moulted the entire body appears shining and reticulated.

Eyes black. Antennae blackish excepting segments I, II, and basal half of
III, which are pale, reaching a little beyond the middle of the body; segment
III longest, it being a half to three-fourths longer than VI filament; segments
V and VI base with the usual distal sensoria. Beak reaching to coxae of second
pair of legs. Legs pale with dusky joints the tips of the tibiae and all of the
tarsi black. Cornicles pale with tip dusky, slightly swollen towards the tip and
constricted just before the apex, and noticeably longer than the cornicles of A.
brassicae. Cauda conical, and dusky to blackish.

. THE TURNIP LoUsE.

nun,”

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Wax

Fig 2——-The Turnip Louse, Wingless viviparous female. (OriginaL)

Measurements are as follows (averages from six individuals): Length of

body, 1.66 mm.; width, 1.00 mm.; cornicle, 0.226 mm.; cauda, 0.140 mm.;
antennae I, 0.080; II, 0.061; III, 0.399; IV, 0.202 mm.; V, 0.160; VI, base,
0.122; VI, filament, 0.287; total average length, 1.311 mm.

Papa.

Head dusky, remainder of the body cream color or with a faint greenish
tint, and covered" with a slight whitish pulverulence, excepting the shining
areas, which are covered with a noticeable reticulation, and which are placed
as follows: A row of oval or transverse areas on each side of the median dor-
sal line and a row of smaller and more circular ones laterad of these on each
side, about in line with the cornicles.

Eyes black. Antennae pale dusky, the distal ends of segments being more so,
relative lengths of segments as in the winged female. Wing pads blackish. Legs
pale dusky with the joints, distal end of tibiae and tarsus blackish. Cornicles

26 TEXAS AGRICULTURAL EXPERIMENT STATION.

dusky, paler at middle, blackish at tips, and similar in shape to those of the
Wingless female.
' IVinged I7’i7j'l‘pd7”OU8 Female.

Head and thorax black. Abdomen pale apple green with a tint o-f nile green
and a row of three black spots on each side anterior to the cornicles; a. row of
small impressed dots 0n each side dorsad of the larger spots; and in addition
a few scattered inconspicuous dusky markings on the dorsum, and the last
three segments with black transverse dorsal median markings.

Eyes black. Antennae black; almost reaching to base of cornicles; segments
III a11d VI filament subequa-l; segment III With 19 to 26 moderately tubercu-
late circular sensoria irregularly placed, IV with 6 to 10, often more or less
in a row, V and VI base with‘ the usual distal sensoria and not infrequently
segment V bears one or two near the base. “7ings with black and rather con-
spicuous veins, and the terminal branch of the media nearer the apex of the

 

Fig. 3—The Turnip Louse, winged viviparous female. (OriginaL)

wing than where it first branches. Legs with femur pale brownish t-0 blackish,
tibia pale brownish with tip black and tarsus black. Cornicles dusky, paler at
tips, and shaped as in the wingless form. Cauda concolorous with the abdomen
or paler. a » -

Measurements as follows (averages from six individuals): Length of body,
1.4 mnr; width of body, 0.66 mm.; length of wing, 2.4 mm.; width of wing,
0.9 mm.; antennae I, 0.069; II, 0.061; III, 0.363; IV, 0.191; V, 0.165; VI,
base, 0.126; VI, filament, 0.358; total average length, 1.333 mm.; length of
cornicles, 0.172 mm.; of cauda, 0.134 mm.

Humidity.

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'l1011B.I9I19{) qwg
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110118191199 1118K
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110112191199 191g
'11011B.19L19Q 11103
"uogmaauag 11151

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‘110113191199 LIIQI
110118191199 IIIQI
110118191199 1.['1I7[
'I1011B.I9119{) 

TABLE 11.

THE TURNIP LoUsE. 27

 

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flmWWW& Nwwhmwwhhwmmhwwmwohwhhmwwmmmwowmmom

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First-born Generation Series.

‘110113191199 1119

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2nd

   

Temperature

 

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2s

TABLE II-Continued.

First-born Generation Series.

Humidity.

TEXAS AGRICULTURAL EXPERIMENT STATION.



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.21

 

Temperature

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110112191199 11117
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: : : : : : . . . . : —<—1

 

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Date.

 

29

THE TURNIP LOUSE.

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3O

TABLE II-Continued.

First-born Generation Series.

Humidity.

TEXAS AGRICULTURAL EXPERIMENT STATION.

‘WRIIIIIIIW

umwgxnw

110112191199 11199
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101112191199 p199

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Temperature

 

Date.

. - mwmmmmwmw~wnw
wmwmw & mmwwwmmmmwmmm
. - mm mmmom mwh
m“wWWN¢% @w§hwvmw§nwm

 

 

31

THE TURNIP LOUSE.

 

 

 

:mmw~Nmmm

mommmm

  

MP-WVMNfiOOOQKOOOMMkONONNCYJm

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mm S.
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3 $
Q 8

Quofi. .Q 2:3 d

  
   

$.54

32

T ABLE II——Continued.

Humi ity.

TEXAS AGRICULTURAL EXPERIMENT STATION.



‘umuxgxe W

‘UOEIBJQUSQ’ 

"uoqelauag 111179
"uonmauag plgg

110118191139 

'u011e.1aua{) 1s 1g

‘uogwlauag 11199
‘IIOHB-IQUQD ‘H68
‘uogualaueg I11gZ
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‘uonelauag 11193
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First-born Generation Sefigsf

‘110112191199 I119
_ 10112191199 111g,
110118191199 
uoneiauag 111g
TIOFIE-ISUQQ 
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mm

Temperature

‘UOEHZJQUSQ 1S'[

VITIWIUEW Ho

‘UIIIIIIIXBW '30

Date.

olodwilokdfiodcid
Vfi

33

THE TURNIP LQUsE.

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. . . ¢ - . . . . - - - . - . . . . . . - ¢ - - .

. - . . - Q . . . . . . . - . . .

. . - . - . - . . | - ¢ - . - - - » - . . . - . . . . . - . - . .~

‘ . - . - - - . - ¢ - Q ¢ - - . . . . . . - . . - . - - . . ..

- . - - - . . - - .

. . - . . . . . . - - . .

| . . - - . - Q . - - ..

. . . . . . ¢ . . . . . . . . . .

. - ~ . . - . . - - . - . - . . .0

. . . - - - . - . . . . - - - . . - . ¢ . . . . . Q - . - ¢ . - -

. - . . . . - - . . . . - . .-

. . . . . . . . - - - - . - . . .

. . . . . . . . . . . . . . . . . . . . . - . - - . . - . . . .

. . _ . . . . . . . . . . . . . . . . . . ..

. . . - . . . . . . . . . . . .

. . . . . . . . . . - . - - - . n

. . . . . . . . . . . . . . . . . . . . . . . . . - . ~ . . . . . Q - ¢ . - . . . . . . . - - . . . . . . - . . - . . . . . . . . . . . . . . . - - - . . - ..

. . . . . . - . . . . . . . .-

60% .Q :22 .m

wash

34

TABLE II—C0;1tinue d.

First-born Generation Series.

Humidity.

TEXAS AGRICULTURAL EXPERIMENT STATION.



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35

THE TURNIP LousE.

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36 TEXAS AGRICULTURAL EXPERIMENT STATION.

MOULTING.

The process of moulting is much the same in A. pseudobrassicae, as
is elaborately described in Webster (l.c.)t for Tozvopterrai gram/inuim,
Bond. Accurate records have not been kept upon the actual time re-
quired for the lice to moult, but the processes necessary for the louse to
liberate itself from the old skin have been constantly observed. Records
have been made continually throughout the lite history studies upon
the number of moults and the periods between them. From these ob-
servations it is evident that the ivingless and winged lice moult four
times. The following table is taken from the records to show the char-
acteristic features of the periods of moulting in this species:

TABLE III——SHOV1-NG MOULTS OF WINGLESS LICE.

_ - Produced
Date of Birth. M—1* M—2 M—3 M—4 First Young.
l
Jan 3O .................................................. .. Feb. 1 Feb. 5 Feb. 11 Feb. 14 Feb. 16'
Feb. 16 .................................................. .. Feb. 2O Mar. 4 Mar. 8 Mar. 13 Mar. 16
April 4 .................................................. .. April 7 April 9 April 13 April 16 April 18
May 5 .................................................. .. May 6 May 8 May 10 May 12 May 13
May 13 .................................................. .. May 14 May 16 May 18 May 20 May 21
June 10 .................................................. .. June 11 June 12 June 14 June 15 June 16
June 24 .................................................. .. June 25 June 26 June 28 June 29 July 1
July  July 11 July 14 July 17 July 21 July 24
*M-1--—Indicates the first moult; M—2 second moult, etc.
TABLE IV——SHOWING MOULTS OF WINGED LICE.
f
- Produced
Date of Birth. M—1 l\I—2 M-4 M—4 First Young
Sept, 22 Sept. 24 Sept: 27 Oct. 1 Oct. 5 Oct. 7
Nov. 14 .................................................. .. Nov. 16 Nov. 20 Nov. 24 Nov. 30 Dec. 2

No experiments have been conducted to determine the exact varia-
tion of the length of the instars, but from the many observations made
it is evident that such a variation does exist, even when the individuals
are born at the same time and are kept under exactly the same condi-
tions. ‘This variation is more pronounced during the cooler parts of
the year when there is some considerable period between the moults.

Jan Feb qr Apr Jiuly g ep Oct Nov Dec mew

Fig. 4—Succession of Generations in the Turnip Louse, 1914.

THE TURNIP LOUSE.   37

NUMBER OF GENERATIONS.

In January, 1914, a study of the successive generations of A. pseudo-
brassicae was commenced. This work was continued without a break
until August '7. During the latter month it Was hot and "dry, so the
host p-lants did. not grow well, and the lice gradually died. It is doubtful
if the lice can be raised throughout theyear upon the turnips, since it
is quite probable that there is an alternate host plant. However, the
lice were reared upon turnips in the cages long after they disappeared
from the fields. The cage studies were again started on September
14, the time that the lice returned to- the turnips in the fields. This
series was continued for one year, until September 14, 1915. After

June 23, 1915, radishes were used for host plants, as in the fields the-

lice seemed to prefer them to turnips, which naturally do not grow well
at this season of the ‘year.

F S OCT V D

l4

Fig. 5—Sucoession of Generations in the Turnip Louse, 1914-1915.

N o sex forms have ever appeared in the cages, and only twice have
winged agamic females developed in the cages. The sex forms have
never been observed in the field, though a search was made for them
in the extreme northern part of the State.

The generation series given in Tables I and II are of the first born
individuals only, and give but the maximum number of generations
which may occur in a given time. There will naturally be a variation
in the number that will occur in a year, as there is a variation
in the life history of the individuals. From January 18, 1914, to
August 3, 1914, twenty generations were obtained in the cages. From

38 TEXAS AGRICULTURAL EXPERIMENT Srxrioiv.

September 14, 1914, to September 14, 1915, thirty-five generations
were secured. These experiments Were conducted out-of-doors, under
as nearly; natural conditions as it Was possible to imitate.

AGE AT WHICH THE FEMALES BEGIN REPRODUOING.

Climatic conditions, and especially temperature, exert a very great in-
fiuence upon the age at which the lice begin to reproduce. In January,
1914, the average time from the birth of the louse to the date of its first
offspring was 12 days, during February 1'7 days, March 13 days, April
12 days, May 8 days, June 5 days, July 11 days, September 11 days,
October 12 days, November 10 da.ys, and during December 1'7 days.
In January, 1915, the average time of this period. was 21 days, in Feb-
ruary 1'7 days, in March 23 days, in April 9 days, in May 6 days, in
June '7 days, in July 6 days, and in August 8 days. The greatest

length of this p-eriod occurred during the latter part of February and.

the first half of March, 1914. The shortest period, 4 days, occurred in

June, 1914. .
REPRODUCTIVE PERIOD.

The climatic conditions exert a.s great an influence upon the repro-
ductive period as they do upon the age at which the lice begin to re-
produce. The total number of offspring is less during the cooler parts
of the year, but during those months when the total number of young
produced is about the same April and May, and September and. Oc-
tober—the length of the reproductive period is longer when the tem-
peraturc is low. In February, 1914, the reproductive period was 24
days, March 1.9 days, April 19 days, May 1'7 days, June 14 days, July
15 days, September 19 days, October 19 days, November 15 days, and
during December the period again exceeded 31 days. In January,
1915, the reproductive period ‘exceeded 31 days and extended into Feb-
ruary. In February this period again exceeded the month, and also in
March the reproductive period extended over more than a. month. In
April this period was 22 days, May 15 days, June 18 days, July 19
days, and in August this period was again more than a. month. The
greatest period of reproduction occurred during the months of Decem-
ber and January. The shortest period, 12 days, was during the first
half of June, 1914.

39

THE TURNIP L0 USE.

. . . . . . . . . . . . . . . . . . . . . . .. N3  1.... .........-.-.¢x 

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mm w3 E33. w +m.m mm 33 33 >333. 3. 3 >333. 0m v53. ........... ..wm v53.
mm 33 E3. 3. + w.m wm 3.3 03 >333. w wm v53. mm v53. .............. ..0m v53.
wm m3 E33. w +m.m 3w mm m3 E3. w 0m v53. 0m v53. .............. ..m3 v53.
mm m E33. 0 +m.m 3.w m3 3 >333. m m3 v53. m3 v53. .............. ..03 v53.
3m mm v53. w +3..m m3. m3 mm v53. 3. 03 v53. 0 v53. ........... ..m v53.
03 m3 v53. 33 +m.w m03 m3 w3 v53. m m v53. m. v53. .............. ..wm >32
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mm w v53. 03 +m.3. 303 w3 m v53. w 3m >32 0m >32 .............. ..m3 >32
mm 0m >32 0 +3..m 3.0 3.3 0m >32 w m3 >32 m3 >32 .............. ..m >32
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mm m3 333334 33 + 0.m m0 03 m3 333334 m3 wm .332 mm .332 .......... ..m3 H332
3w m 333334 w 0.w m3. 03 m 33.3334 3.m m3 .332 m3 .332 ............ ..m3 339.3
mw m3 .332 m +w.m. wm 3.m w3 .332 3.3 m3 .33vr3 m3 .33v...3 ............ ..0m M333.
wm wm .3393 w .|m.m 03. wm mm .3333 m3 0m .333. 0m .333. .............. ..w3 3303.

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m>vm3 33303. ..o333vw3 .30 30D .30 33.303

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4O TEXAS AGRICULTURAL EXPERIMENT STATION.

. . - . - - - . . - . . . . . - - ~ - - . - . - - - - - . - o ¢ ¢ - - - ¢ - - ¢ - . . - - - . - - - . . . . . . . - ~ - - - - - - - . . - - . ~ . - - - . - - . - - . ¢ . . - - - . . - - - - . . - . - - ~ - . . . . . . . . . . - . - ¢ - . . - - - - - . - . - ¢ | - - . . . - . - . - . - - . . . . . . . . . - . . . - . . . . - - - . . . . - . . . . . . - . . . - - . . . - - - - - - u ¢ - - ¢ - - . - - . - . - - . - - . - -¢® 

Q . . . . ¢ . - » - - - . ¢ . . . . - . . . . . . - . ~ . - - - . - - - . - . . - . - . Q - - - . . - . . . . - - - . - - . . - . . . . . . - . . . . . . . . - - . . - . - - . . - . . . . . . - . . . - . . - . . - . - . . Q . . - . . - - . - . . - - - . . - - . - . . - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. w m  w  1......- .....m 

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. . . . - - . . . . . - . . . . . - . . . . . - . . . . . . - - . . . . . - . . - . - - . . . - . - - - - - - - - - ~ - . . . - - . . . . . . . . . . . . . ...|-.....:-..... ......-.-...--........ ....-...-............. ........-...............      ....-.........©? 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. @  .w5<  -w5.<  .w5.<
mv o3 03m m +w.m 3w mm w 000w w w 0:4 N. .m:4 ............ ..3m >33.
mv v 0.00m v +m.m mN. vm m 300w w 3m >33. om >33. ............ zwm >33.
d. N0 .00.... w +0.0 R S 3.0 .03. N. m0 >33 3.0. .23 ............ .2 >35.
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om m >33. N. +w.v wm 3m 3 >33. w 33 003. 2 2:3. ............ ..w 2:3.
wm m3 0:3. w ||m.w mm w3 w3 2:3. w m 2:3. m 2:3. .............. ..wm >32
mm m3 2:3. 2 0.0 mo3 N.3 33 2:3. w wm >32 wm >32 ............ ..3m >32
vm v 0:3. 2 o.N. 02 v3 m 0:3. m 3m >32 om >32 ............ ..m3 >32
wm wm >32 33 +v.w mo3 w3 N.m >32 w m3 >32 m3 >32 ............ ..w >32.
mm mm >32 o3 +v.w mo3 w3 m3 >02 N. w >32 v >32 .............. ..wm33.:34
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wm w >32 w 0.0 mo3 N.3 v >32 w w3 33:34 N.3 33.54 .............. .2 33:34
wm m >32 w +m.v mo3 mm 3 >32 m3 2 33:34 m 33:34 ............ ..mm Q32
wv m3 33:34 N. + m.v mo3 mm w3 33:34 wm mm Q32 wm Q32 ............  Q32
N.w m3 33:34 w +w.m mo3 ov 33 33:34 w3 m Q32 3 Q32 ....  ....... ..w3 43003
oN. N. 33:34 w .|3.m vo3 ow w 33:34 m3 w3 bob m3 3on3 ............ ..N.m d3.
vw m Q32 v ||3.m mw ov w Q32 mm N.m d3. wm d3. ............ ..w .d3.
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mw 3m d3. v +3.m wN. Nm om d3. v3 w3 .0oD v3 .00D ............ :3 00D
mw w3 d3. m +N..3 ow wv v3 d3. N.3 3 .00D om >02 ............ ..v3 >02
3v w3 .00D N. +m.m mo3 3m v3 .0oD m v3 >02 m3 >02 .............. ..w .>02
mm om>02 2 +m.w wm w3 m3 >02 w w >02 v >02 ........ zzzzom .300
N.m m3 >02 o3. +v.N. wm m3 33 >02 m3 om .300 mm .000 .............. ..N.3 Q00
mm m >02 w +w.w mm N.3 m >02 33 N.3 .300 2 Q00 ............ ..w .300
wm Nm .000 N. +0.3. wm 3m wm .300 v3 w .300 w .300 .............. zmmQdow
wm 33 .300 w + m.w 02 m3 2 .300 w mm 230m 3m .300 .............. ..v3 230w

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.30 30 030D 52:30:02 000.303. . 330.3. 023030 00013 .w>0D .0w4 323m 30 030D .30 030D
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.0303-E2|mzoQ.3.<dmz3.3w .330 @2331; H3334?

THE TURNIP LoUsE. 41

LON GEVITY.

The life of this louse is much longer in the spring and fall than in
the summer, but is longest during the ‘winter months. During this
time a single generation Inay live over a considerable period of time.
The length of the life of a generation upon the alternate host p-lant
may vary much from that ascertained when turnips were used. The
length of the life of each generation is shown in Tables V and VI.

AVERAGE NUMBER OF YOUNG DAILY.

The averages here given are made from the total number of young
produced during the reproductive period of a. generation. During
January, 1914, this daily average was 1.8, during February 2.5, March
4.1, April 5.0, May 6.4, June 6.0, July 2.3, September 4.8, October 5.4,
November 6.2, and during December 2.2. During January, 1915, the
daily average was 1.9, February’ 2.1, March 2.5, April 5.0, May 6.7,

June 5.4, July  and August 2.3.

RATE "or INCREASE.

To those who are not familiar with plant lice it seems strange, in-
deed, that a turnip patch can be destroyed in such a short time by lice.
When the rate of reproduction is known, it is possible to appreciate
how the lice can increase in number so as to destroy a. field of turnips.
Many estimates have been made on the possible reproduction of plant
lice, and the numbers obtained are so large as to be beyond meaning

I to the human mind. The turnip louse is among the most prolific of

the plant lice. In the cage experiments 35 generations were obtaine-d

in twelve months. None of the lice produced less than 25 young, and

most of the females gave birth to 80 to 100 young each. The greatest
daily reproduction was 12, but 8 p-er day was not uncommon, and 6
young was very frequent. It is not surprising, when these figures are
considered, that if a few lice are left when the turnips are sprayed, the
plants will be covered again in the course of a few days.

The following table gives the comparison of the reproduction in the
winged and Wingless lice. ’l_‘he table sho-ws that the reproductive period
of the winged lice is shorter than that of the Wingless lice. The daily
number of offspring is less in the winged lice, and of course the total-
number of young produced by them is much less than the number pro-
duced by the Wingless females. I a

42 TEXAS AGRICULTURAL EXPERIMENT STATION.

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.=:=.=¢==.:==.==;.¢.@ ....................... .. N NN N“ .====H ..... =NM
............................................................. .. N NN N“ .========NM
.;==.z==.=s¢.=s;.=H .......................... = N “N N“ ................ =NM
===;.:==.=s=.==;=.@@=.JJ ................... .. N MN N“ ................ ;NM
====.===.===;.¢:=.===.»@ .................. .. N N“ NN ................ ¢NM
====.===.=s;.====.===.H .................... .. “ N“ NN ................ =MM
====.===.====.===.=;@~.@-.~HN»M:=~. N N“ “N .;¢==@~»~NM
===;.===.==;=.===.===;.;=.H==H. =~.. “ N“ “N .;=;=».@=N
====.===.====.==1.====.=-..==N=.»... “ N“ NN .;=:=NH@.N
.===.====.:;=.===.===:==@@.;=@.»;». “ NN NN .==@»v~HN“
N N u - ¢ . N - . N N N . . ¢ Q o N - - u - - u - - . . . - - N N u N N ¢ N N N N . . . Q N - . .. w   ...... .. Q w
       ..........  NN NN ................ N
.=:=.====.==~H====.==@H==@n.=@~H~H~H ...... .. NN NN .=@-m-~N
.......... ===.==¢.====.===.=. .=.. . .===. NN NN .=.. ....N
.===.==.=.=. .====.:= =H ........................ .. NN NN .=¢. =H. N
    N.    ..H ..  ..................... .. NN N  N. N 2N
==== H ................................... . . NN MN ............. ..NN
.......................................................... .. NN “N .=¢;¢s===NN
.................................................................. .. NN NN .====s===NN
.................................................................... .. NN NN .==;=:===“N
...................................................................... .. “N NN O::::5:::®N
nuwm .............................................................. .. NN NN .===s=»= NN
................................................................. .. “N NN .===s=.==NN
.H .......................................................... ... ..... .. NN NN ................ =NN
. . . . . . . . . . . . . ...-.....- ...-.... ........ ........ ........ .-.-... m   ..................NN 
_ _ N NMNM
N N _ “ N _ N _ N _ N N _ M Mawn .NNNN
.NNNNN
NNBmMNFNP diam.

fioMq WwHAUZUF QZ< nmwzrs ZN ZOFHODQOMHHMIQN» HAHNNE.

43

THE TURNIP L0 USE.

62w .Q 2Com .m £333: .2

.2 ......... ....... . 1...... ........ ...... . . . . . ..... ........ ........  ¢ m @...Y>   ........£...l....#.m

fi ........ .... . . . . . . . . . . . . . . . . . . . . . m @ . . . . ..   . . . . . . . . . . . . ..§.—.

é . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . .. x N .... ..   . . . . . . . . . . . . . . . . ..@

fi . . . . . . . . . ... . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. an... @ . . . . . . ..   . . . . . . . . . . . . . .... fi

Aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. @ @ . . . . . . ..   . . . . . . . . . . . . . . . . lib

% . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . . . .. @ § . . . . . . ..   . . . . . . . . . . . . . . . . ..@

fi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. § @ . . . . . . ..   . . . . . . . . . . . . . . . . ..@

Aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. fl m . . . . . . ..   . . . . . . . . . . . . . . . . law

aw . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. m m . . . . . . ..   . . . . . . . . . . . . . . . . Dim

aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... x @ . . . . . . ..  .  . . . . . . . . . . . . . . . . ..@

Aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. x Q . . . . . . ..   . . . . . . . . . . . . . . . . 1.x Khfiwm

Aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. x W . . . . . . ..   . . . . . . . . . . . . . . . . ...mm

Av . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. fi x . . . . . . ..   . . . . . . . . . . . . . . . . 

@ . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .w @ . . . . . . ..   . . . . . . . . . . . . . .....@§

.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. é N . . . . . . ..   . . . . . . . . . . . . . . . . 

.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. fi § . . . . . . ..   . . . . . . . . . . . . . . . . 

Aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... . . . . . . . . . . . . . . . . . . . . . . .. Aw N“ . . . . . . ..   . . . . . . . . . . . . . . . . 

Aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  @ . . . . . . ..   . . . . . . . . . . . . . . . . ..@Nu<

_@        ........  .  @ . . . . . . ..   . . . . . . . . . . . . . . . . ..$@

aw .... . . . . . . ......  2...... ........ ........ ........ ........   . . . . .. 3 . . . . . . ..   . . . . . . . . . . . . . . . . ..Ah...@

@ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. @ ...... ..   . . . . . . . . . . . . . . . . 

fi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. @ . . . . . . ..   . . . . . . . . . . .... . 

M .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... . . . . . . .. ........ ........   fi ........   . . . . . . . . . . . . . . . . ..@@

.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. @ . . . . . . ..   . . . . . . . . . . . . . . . . 

fi 1...... 2......         x . . . . . . ..   . . . . . . . . . . . . . . . . 

x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. fi . . . . . . ..   . . . . . . . . . . . . . . . . 

.m . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. @ . . . . . . ..   . . . . . . . . . . . . . . . . ..@.m

Aw ........ ........  ........  ........     w . . . . . . ..   . . . . . . . . . . . . . . . . OlmH

Aw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. M . . . . . . ..   . . . . . . . . . . . . . . . . 

fi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. @ . . . . . . ..   . . . . . . . . . . . . . . . . 

M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Q . . . . . . ..   . . . . . . . . . . . . . . . . 

w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. fi . . . . . . ..   . . . . . . . . . . . . . . . . 

o ........ ........ ........ 1...... ........ 1...... ........ ........ ........ .....>F .? . . . . . . ..   . . . . . . . . . . . . . . . . 10%

M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. fi . . . . . . ..   . . . . . . . . . . . . . . . . ..@

a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. fi . . . . . . ..   . . . . . . . . . . . . . . . . 

.2         ........  fi . . . . . . ..   . . . . . . . . . . . . . . . . 

é . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. M . . . . . . ..   . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2    

2   2......          . . . . . . . . ..   . . . . . . . . . . . . . . . . 

im  . . . . . . . . . . . . . . . .  Scflk.

            . . . . . . . .. 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..   ................>..FAW.
o..o.... q-n-a... .a.n-¢. .n..nu-| o...¢... .....u¢. |...¢|.- ....-o. .|..~.o¢ ...a|... 1.0a...- ........ ....ii.5   ....u.uu....iiL>o@om
. . . . o . | u . . - - o . . . . ¢ a n n Q . . . . . . o . ¢ u . . . . . . . . . . . . . . . Q . . . . - v | . Q ~ o . u o . . u . ¢ ¢ - n ¢ u . u . u . . . . Q . . ~ u . . . . . . . o . . - . Q ¢ 0 -   ............ 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..   

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..   

                   . . . . . . . . . . . . . . . . . ..   . . . . . . . . . . . . . . . . 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..   

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..   

TEXAS AGRICULTURAL EXPERIMENT STATION.‘

mm mm .............................. .. H o .............................. .. .. . ...........  .. ............ .. H» m ............... .. .. a» wm wmmmmmmmmmmmN

mm  . - . . - . . - . . . . - . . - . - . - - . . - . . . ¢ . . o. N .? . » - . . . . . . - . . . . . - . ¢ - - - . . . . . ~ . - . - - . - . - . - . - . . . - . . . - - . . - . - - - . . . - . . - . . . . . . . II w fi - - . . . . . - . . ¢ » - . - . - - . - . - :   . ¢ . . . . - . . . - - . . . . Iwfl

ofi  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .€ fi . . . . . - . - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. x m . . . . . . . . . . . . . - . . . . . . . . ..   . . . . . . . . . . . . . . . . 

mm om .............................. .. H H ...................................................................................... .. m m ...................... .. mm mu . . . . . . . . . . ..HN

Hwm ooH .............................. .. H H .........................................  .......................................... .. H H . ...................... .. Hum hm . . . . . . . mN

om vw .............................. .. H H .........................  .......................................................... .. N N ...................... .. “N ww .........wmmmwmmNN

mN Nw .............................. .. c o .........................   ................................................ .. H H ...... ... ............. .. Hwm av ........ .. HN

mm mw .............................. .. o o ...................................................................................... .. N N ...................... .. Hm mm ................ oooN

Nm ooH .............................. .. H H .............................  ...........  ........................................ .. N H ...................... .. NH~ mo ....m...m...mmmmmmmH

mm ooH .................  .......... .. H o .........  .......................................................................... .. m. m ...................... .. mm. mu .......... .. wH

on mm .............. .. .. . .......... .. o o ...................................................................................... .. H N ...................... .. mm mm .............. SH

mv mm .............................. .. o H . ..........  ...................................................................... .. H H ...................... .. om mm 

Hv ooH  .......................... .. o o  .....................  .......  ......  ....................................... .. m w. ...................... .. wv mm ........mmmw..mmmH

um mm .............................. .. o o A .....................  .. . .. ..........  ................................. .. w m ...................... .. 0H» on . . . . . . . . . . . ..H~H

Hw wm .............................. .. H>H o o .............................................................................. .. m. N ...................... .. ow Nw ........... .. mH

Qm ww ...................................... .. H>H o .........  .................................................................. .. m N ...................... .. wv Nw ................ ..NH

Q mm      ...... .. H .............................................................................. .. N . N . ..................... .. Hwm on ................ ..HH

mm mm     zmfi ....... .. c .............. .. .. ...................................... .. H . H  .............. .. mm 3 .............UmmmmoH

Hfi ooH ........................................ .. o . . . . . . . . . . . . . . . . . . . . . . . . . . . .  .............................. .. H H Q .............. .. Nm wm ........... .. a

mo Nw     .m...m ........ .. o .. .............  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. N H H .............. .. mm ow 

om mm ............................... . mwwm  o .............. .. ... .. .............................. .. N H H .............. .. mm aw .....m..mmmmmmmm..h

mm am ..................................... .. o ...........  ...... .. . ..................................... .. N H H ........  HHN mw ..... .. w

mm ooH .............................................. .. o AH ..  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... ..... .. m o H .............. .. mm mm 

Nm ooH ..........  ......... ... ....................  N o  ...... .. . . .................................... .. m N N .............. .. om Hvw  ..m w

wm ooH .................    ...... .. o o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. o N m .............. .. aw Hw ........ fifiLm

mm. ooH ............................................. .. H m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. H>H N N .............. .. mv Hm ......  .... ..N

av ow .................  .......................... .. o o  .....  ..........................................  H H ...... .. .. .... .. mm mm.  ..... .. H .32

mw mm .............................................. .. c o .............................................................................. .. H H .............. .. mv mm  ........ zwN

Ev ooH .................................  .......... .. H>H m  ...................................................................... .. N m. .............. .. mv mo ................ ..NN

ow ooH ...................................................... .. N    ....................................................... .. H N .............. .. wv vm . ............... zwN

mm Na .............................. .. . .  ...... .. N  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  ........................ .. m N  ......... .. NH~ no ................ zmN

mm wm ...................................................... .. o .. ......  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. H m .............. .. wm mw ................ ..HN

mv aw ...................................................... .. o . .......  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. N H ..........  ow Nw ................ ..mN

wN mm ..................  .............................. .. N  .......................................................................... .. N m .............. .. mm Hm ................ ..NN

m» mm ....... . .. ............................................ .. m ...... .. Q .............................................................. .. N N  .......... .. mm aw ................ ..HN

Hvw mm ...................................................... .. N ...... .. o .............................................................. .. N A N .............. .. mm Hvw ................ ..oN

ow ooH ...................................................... .. N .. .... .. o .............................................. .. m N .............. .. Hm o». ................ 6H

Hww mm ...................................................... .. N .. .... .. H .............................................. .. H N .............. .. uv ww ................ uuwH

HH» mu ...................................................... .. N .. .. H .............................................. .. N N .............. .. Hmv we ................ SH

mN ww ...................................................... .. o nH H ................  ........................................... .. N N .............. .. HHN on ................ zwH

mm ww .........................................  .......... .. H o H .............................................. .. N N .............. .. mv ww ................ ..mH

Nm wm .....................................  .............. .. H o N ................................................ .. o N nH ...... .. mv on ................ ..H\H

Nm ooH ...................................................... .. H H m ............................................... .. H>H m N ...... .. mm H“. ................ ..mH

m@  .... - . . . . . . . . . . . . . . - - . :4 . . . . . . . . . ...-...? . . . - ... - . . . - . . I o i N . . - . . . . . . ... . . - . - . . - - . . . . . - . . . . . . . . . - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. % N . . . . . . ..   . . . . . . . . . . . . . . . . ..N.P
.=_._2 J32 x . m _ a w _ H Q _ w o A w. HH 2 m w v @ m w m N H .52 5W2 $2.5
SHHHVHEQHH .. domfik/ dwfiwfik/ . diam.

44

Auo-HEEHQUIIHUHH QMHAUZHB QZ< QHUZEF Zn ZOHFODQONHHiIHEr HHMHFH.

45

THE TURNIP LOUSE.

 w HHHHHHHUHHH
no-Onuol m n - o u Q - Q u Q on
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...... .. w  
00000000 m ¢ Q I Q o u u 0 - n o Q no
u o 0 0 Q u an N uuou-uo- cannons:
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ma“  HMH 
.............. .. Q 
.............. .. o 
.............. .. w 
.............. .. w 
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.............. .. w Q
.............. .. w o
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...................................... .. w w 
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.....        w w  
....   w a 
.............................................................. .. w w 
.............................................................. .. w w 
.............................................................. .. w w . .. 
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.............................................................. .. w w 
.............................................................. .. w w  
.............................................................. ..  w a ..
.................................................................... .. w w 
.................................................................... .. w w 
................................................................... . . w w w
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...................................................................... .. w.... w w
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THE TURNIP LoUsE. 47'

EFFECT OF TEBIPPIRATURE ON DEVELOPh/IENT.

The winter of 1913-14. presented many unusual climatic conditions
and afforded an excellent opportunityto study the effect of Weather
conditions upon the habits of the lice. On January 1'7, 1914, when the
generation experiments were started, the weather was warm. At this
time the females were producing from 5 to 8 young per day. For
some time previous to this it had been quite cool and the increase in
temperature stimulated reproduction and the females responded very
quickly to the changes in temperature. On the night of February 6,
1914-, the temperature suddenly fell to the unusual p-oint of 17° F.
The next day was cool, and the following night was quite; cool, 32°, b-ut
the following day was much warmer. On this day the females under ob-
servation gave birth to a.n average of 2 young. Several winged lice
also developed on the plants in the cages. During the week of Feb-
ruary 10 to 1'7, 1914, two quite- hard freezes occurred, but the days
were warm. The daily reproduction did not seem to be seriously
affected by the low night temperatures. Winged females continued to
develop- in the cages during this time. The latter part- of February
was quite cold for a period of a week. The reproduction at this time
uras very materially reduced, and but few winged females developed in
the cages.

During early March a patch of turnips was artificially infested with
A. pseudobrassicae. At that time it was quite warm and the females
soon became established upon the plants. Within a week after the lice
were transferred, good-sized colonies were found around each female.
Reproduction materially increased during the warm days and decreased
on the cool days. The period from March 20 to 3O was cooler
than the preceding two weeks and the drop in reproduction was very
noticeable. The warm period which followed caused the daily repro-
duction to go up from 3 or 4 to *7, S or 9. April 7 to 12 was
again cool, and. the rate of reproduction drop-ped to 2 young per day.

SUMMER REPRODUCTION.

During the summer months the reproduction is low. When the hot-
test days of the summer occur there is no reproduction, even for days
at a time. It is quite evident that the summer conditions are much
harder for the lice to withstand than are the winter conditions.

OTHER SPECIES FOUND.

There are two other species of plant lice which may be found upon
thesame plants on which the turnip louse feeds. Very often one or
both of the species have been taken upon the plant at the same time.

The cabbage louse, A. braasicae Linn, is often found upon cabbage,
especially in the fall, and is often mistaken for the turnip louse.
Wherever the cabbage louse is found it is a serious pest upon the plants
attacked. The cabbage louse is known to» feed upon most of the known
host plants of the turnip louse. In Texas the writer has observed the
cabbage louse upon plants other than cabbage but once; in the spring
of 1915 a few colonies were‘ found upon turnips. In the past it has

48 TEXAS AGRICULTURAL EXPERIMENT STATION.

been thought that the cabbage louse was responsible for the injury to
winter turnips, and there is no doubt that the turnip louse has not yet
been recognized in many sections. In reply to inquiries, several ento-
mologists stated that the cabbage louse was known to be present and
that the winter turnips suffered from the attacks of a. plant louse.

It is a. comparatively- easy matter to distinguish the cabbage louse
from the turnip louse. This is especially true of the wingless female,
which in the case of the cabbage louse is covered with a cottony sub-
stance, whereas the turnip louse is bare. The winged females of the
cabbage louse have distinct. transverse bands upon the abdomen, which
are not found upon the turnip louse. .

The Green Peach-Aphis, Myzus persicae Sulz, sometimes called the
“garden aphis,” has very often been found upon turnips, and by some
has been mistaken for the turnip louse. The variation in appearance
and the great range of host plants has caused much confusion in the
determination of this species. The synonyms of this species are listed
by Gillette,* who also describes the various forms. _ Those forms which
have been taken during the investigations on the turnip louse arecalled
by Prof. Gillette the apterous viviparous female, second generation and
the spring migrant. This species is most always present upon turnips
and radishes, though never in sufficient numbers to do any injury.
The louse was present in numbers in the out-of-door cages during the
winter of 1913-14. This species is much more hardy than the turnip
louse, though it is not nearly as prolific. During the winter the low
temperatures did not affect the garden aphis nearly as much as they
did the turnip louse. During the fall of 1913, when the, fungus dis-
ease, Eampusa, was working such destruction of the turnip- louse, the
gar-den aphis was not attacked until most of the turnip lice were de-
stroyed. Under such conditions the garden aphis served to carry over

the fungus until the turni louse againa. eared. The arasites which c
D p u 7

were abundant, did not. attack the garden aphis until the food supply
of the turnip lice was almost exhausted. Only when the turnip lice

c were about gone would the coccinelids feed upon the garden aphis. The

garden aphis was always found very closely ‘associated with the turnip
louse, the colonies of the two sp-eciesbeing often intermingled upon the
same leaf. ' l

The young of these two species are quite similar in general appear--
ance under casual observaton. The apterous females of the garden
aphis are pale green in color with no markings upon the body, though
occasionally the eyes of the young appear as pink spots on the abdomen.
The general shape of the body of this species is much elongated. The
winged females of the garden aphis closely resemble the turnip louse
at first appczii-ance, but when the two species can be closely compared
it is found that the former seems much darker, dueto the presence of
several black lines across the HlNlOHIQH. The body of the winged form
of the garden aphis is elongate, as are the Wingless forms.

*Journal of Economic Entomology, Vol. I, No. 6, p. 359.

THE TURNIP LoUsE. 49

NATUB. AL ENEMIES.

The enemies of A. pseudo-braszsicae .are not a. few, and the assistance
which they give the grower can hardly be estimated. These enemies may
be grouped into parasites, 0r enemies, which develop within the body of
the host, predaceous enemies, or those which feed upon the lice ex-
ternall , and disease which grows upon "the outside of the lice. There
are twg species of parasites which have been very important in the con-
trol of the turnip louse, D/ieretus rapae Curt, and Lylsipihleibus testa-
ceripes Cress. Other parasites have been taken in the study of the louse,
but they were always present in limited numbers. Of the predaceous
enemies two species of lady beetles, M eigilla maxculata DeG., and Hip-
padmia. c012/z:e1'gen.s* Crueiz, have been very effective in checking this
pest. Syrphid flies and lace-wing flies have been present in limited
numbers. A fungus disease was very effective one season in the con-
trol of the turnip louse.

PARASITES.

Diaeretvrs rapae Curt.

The turnip louse has been very‘ seriously attacked at College Station
by this species of parasite?‘ During the season of 1913 it was present
in great numbers, and was a very important factor in controlling the

pest. It has not been taken at any other place in connection with the a

study of A. f7S8?.i(.?0r7>7‘(lr$8t(‘/(l€. The followring descriptions are taken from
Maryland Bulletin No. 152-, by Mr. A. B. Gahan:

Diaeretus mpae Curt; Aphidius rapae Curt; Trrioarys pieeus Cress.; Aplhidius
brassicae Marsh.; Diraeretus califorvtimrs Baker.

Female: Length 2 mm. Head and thorax black, smooth and shining. Head
transverse not wider than the thorax, the temple-s rather broad and convex, not
sloping abruptly from the eye margin, "clypeus transverse, about twice as wide
as long. Mouth parts reddish yell-ow, the palpi o-ften fuscous. Antennae 13-15-
jointed, (most often 14-jointed), entirely black or dark brown. Parapsidal fur-
rows present at the anterior lateral angles of the meso-notum; pro-podium with
distinct median longitudinal and transverse carinae, the former dividing at
the intersection with the latter and enclosing a short and very narrow are-ola
at the base of the petiole, (this areola. is variable in width, being hardly dis-
cernible in some specimens). Wings hjyaline, veins and stigma brown; the post-
marginal vein and stub of radius are nearly equal, the latter extending about
one-third of the distance to the wing apex; the cubital vein recurrent nervure
and cubital cross-veins are entirely effaced. Anterior legs including their coxae
yellow; median and hind coxae mostly black, yellowish at the apices, their
femora and tibiae brownish; tarsi all fuscous. Abdomen longer than the head
and thorax, often entirely black but usually reddish brown.

Male: Antannae 16-l8-joined. All legs usually dark brown, nearly black.
Abdomen not longer than the head and thorax. Qtherwise similar to the female.

Habitat: United States and Europe.

Host: Aplzis brasstcae Linn.

The details of the life history of. this insect have not been worked
out, but much time has been taken to carefully observe it under field
conditions. ’l"here are a great many points in it which closely resembles

 

*Determined by Mr. A. B. Gahan through the courtesy of Prof. F. M. Web-
ster of the Bureau of Entomology.

50 TEXAS AGRICULTURAL EXPERIMENT STATION.

Lysipheiebus testaceipes Oress., the l.ife history of which is given in
detail by Webster (l.c.).

Egg-laying probably begins Within a few hours a.fter the adult parasite
emerges fro-m its host. We cannot say if the females will deposit eggs
when the males are not present and if these eggs will hatch partheno-
genetically, as is the ca.se with Lysirplzlebzts tastaceipes Oress. In some
cages kept inside during February and March, 1914, the parasites
which emerged gathered immediately on that side of the cage nearest
the ivindow. Here they Were very active, going up the side until the
top was reached, falling to the bottom and starting up- again. Within
the course of a few hours the parasites would return to the louse-in-
fested plant. The manner of oviposition is much the same as in Lysi-
phlebus tesiace/ipes, shown in Fig. '7. While ovipositing the females
seem very excited and act as though they were prepared to make their
escape at any time. Under natural conditions, it is very probable that
only one; egg is laid in a single louse, as in the cages we never observed
more than one parasite developing within one louse.

In January, 1.914, the adult parasites were kept alive for seven days,
though it may be that the adult life is quite long at that time of the
year. In October, 191.3, we were not able to keep the adults confined
in tubes over three days, and most of them died within two days. The
parasites seem to prefer to oviposit in the "younger lice, those which
have passed the second or third moults. Most of the apterous lice
mature and many of them reproduce ‘for’ two or three days, produc-

e ing as many as ten young in a few instances. However, the daily pro-

duction is much reduced in the parasitized lice. Only once has a
winged louse been observed that died from a parasite, and dead pupae
have never been seen. The dead lice seem very securely fastened to the
leaf on which they were feeding before death. A slight cocoon spun
by the larva of the parasite is attached to the body wall of the louse
and, through a hole which has been previously out by the larva, to the
leaf surface. The skin of the dead louse is dull brown in color, parch-
ment-like in texture and seemingly water-proof. We have not been
able to ascertain the number of lice that a single Diaeretus will para-
sitiize, but it is evidently not as many as Lysiphlebus which, according
to Webster (l.c.), averages 94. a

This species of parasite was described from specimens of A. brassicae.
The present experiments have been conducted entirely with A. pseudo-
brass-icae. About May 7, 1914, when most of the turnip lice were
dead, a few Dideretus were taken from Jl/[g/zzas persictae.

Diaeretus was first taken in 191.3 on October 9, when they were
working on the lice feetling "upon turnips. The lice were nearly all
apterous, and the infestation was quite heavy. The first dead lice were
taken just a few days later in the same patch. During the last two
weeks of October but few parasites were observed, though the dead lice
were abundant in all the fields in this vicinity. The parasites seem
to be able to detect a heavily louse-infested area of plants and to move
to it quickly, On November 2, all of the host plants of the lice in a
garden l1ad been sprayed or fumigated, except a few radishesJ Here,
two days later, the parasites were very abundant and hardly a one
could be found around the treated plants. A week later these rad-

THE TURNIP LOUSE. 51

ishes were fumigated and then the parasites were found among mustard
plants, where the louse infestation had just started. By November 19,
1913, fully 2O per cent. of the lice in the College gjarden were para-
sitized. The heavy rains which occurred from November 28 to Decem-
ber 8 killed almost every louse and apparently the parasites.

Diiaev-et/us was next taken on January 13, 1914. In the out-door
cages a few dead lice were seen, making it evident that the parasites
had been present some time previous. The last week in December was
very cold, but the first week in January was mild. Webster (l.c.)
states that Lg/s/iphlebzzs can survive very low temperatures in the full-
grown larval stage. The larvae of Diaeretus must have been nearly
full-grown before the very cold Weather of late Decemb-er and the warm
spell during early January enabled them to pass through the pupal
stage and emerge as adults on January 13. The parasites continued to
emerge over a period of a week. On January 17, more dead lice
were observed upon the cagedplants, which was evidence that the adults
of Diaeretus had been present for some time before. During the first
seventeen days of January the average daily mean temperature was 50°
F., and at this temperature the larval development was not stopped.
Adult parasites emerged from the dead lice collected on January 1'7,
sixteen days later, or on February  During thisperiod the average
daily mean temperature Was 59° F. l

On the night of February 6, the very low temperature of 17° F._

occurred, at which time all of the turnips were badly frozen and 5 per
cent. of the lice were killed. Some of the lice which died from para-
sites four days previous and which were exposed to this low tempera-
ture, were put in a cage inside but with no heat. Eleven days after the
freeze, and fifteen days after the lice died, parasites emerged. They
continued to emerge for a period of seven days. The pupal stage of
this brood of parasites varied from 15 to 22 days, during which period
the average daily mean temperature was 49° F. The reason for this
variation is hard to explain. It is evident that the parasites in the
pupal stage are able to withstand low tempratures and to develop at
low temperatures. The adult parasites were again active in the out-
door cages on February 21, at which time a few lice were observed
and within the next two days manyi were seen. On. March 9, 16
days from the maximum. activity of the last brood, the parasites were
active again. During this period the average daily mean temperature
was 118° F. p

The first Diiaereiivzs taken in the field ‘ivas on March 25. It is pos-
sible that these escaped from the cages and did not survive the winter
in the field. The first dead lice were taken in the field only two days
later, which is evidence that the parasites had been present for some
time before they were observed. The number of dead lice increased
rapidly for a few weeks and threatened the destruction of all the lice
for experimental work. It was not possible to determine the entire life
history, but from the observations made there is a decided overlapping
of broods, especially during the periods of low temperature. The para-
sites were constantly present in the fields until May 13, at which time
most of the turnip lice were dead.

On November 12, 1913, some heavily infested radish plants were

Cu

2 TEXAs   AGRICULTURAL EXPERIMENT STATION.

fumigated with tobacco stems. On the following day many parasitized
lice were collected from these plants and placed in a cage in the lab-
oratory. At the end of a Week a parasite had emerged from every
louse collected. This single experiment confirms the field observations
that fumigation does not injure the pupae within the lice. Of course,
there are many lice with parasite larvae in them, and as such lice dry
up after the fumigation the parasites do not mature.

On November 1'7, 1913, some infested cabbage plants were sprayed
With Black Leaf-4t) and Whale-oil soap. Parasitized lice were collected
from these plants on the day following “the application. ' These lice were
placed in a cage in the laboratory. Within two days parasites had
emerged from all lice in the cage. Our field observations confirm this
experiment, that the soap and Black Leaf-40 sprays do not injure the
pupae of the parasite within the body of the host. The lice which are
struck by the spray dry up at once, and of course the larvae of the
parasites are killed. '

As only one case has been recorded of a winged lou.se being para-
sitized, it is hard to say that Diacretus is disseminated to any great ex-
tent by the host flying from field to field. Webster (l.c.) says that a part,

at least, of the dispersion of Lysip-hlebvis is due to this factor. It is

very probable, hon/ever, that the winged turnip lice are parasitized to
a greater extent than has. been observe-d, which would certainly make
such means of dispersion important in the case of this parasite.

Throughout March, April and May the prevailing Wind at College Sta-

tion is from the South. During these months the wind is seldom in
any other quarter for very long at a time. This south wind is never
heavy, so the parasites may fly safely a great deal of the time. It is
quite probable that Diaercius‘ flies to a considerable extent from field
to field, as they are active in the field at all times when a hard wind
is not blowing. This factor must exert much influence upon the dis-
persion of this parasite.

The temperature exerts much infiuence upon the activity of Diacretus.
During the month of January, 1914, the parasites were quite active in
the outdoor cages when the daily mean temperature averaged 55° F.
Parasites emerged from the lice in February when the average daily

» mean temperature was 53°‘ F., though the adults Were not active at this

temperature. With the average daily mean temperature of 49° F., the
rate of reproduction by the lice was but 2 young per day. Below 49°
F. reproduction is almost negligible, While above this point its rate in-
creases rapid] y. '.l.‘he lice are, therefore, active at temperatures fully 6°
lower than those required for the activity of Diaieretus. During March,
when the average daily mean temperature was 575° F., the parasites
were very active in the fields. During April they were active, ‘with an
average daily mean temperature of 64.5" F. At this time the average
daily reproduction of the lice was 5 young: Whatever start the lice
may have had was soon overcome by the p-arasites in the slightly Warmer

a weather.

The parasites surely do not spread rapidly during times of much
rain or periods of cold, misty showers. A shower followed by sunshine
seems to stimulate the parasites to flight, but a slow, steady rain drives
them to shelter under the leaves of the plants. "

THE TURNIP LOUSE. 53
Lysiphlebus testaiceiipes Cress.

This parasite has been taken in limited numbers from A. pseudo-
brass-icae in our work at College Station. lit has also been taken at
De Kalb, Wortham, McKinney, Iredell, and Hitchcock, Texas. In
these places it was the only parasite present and was usually found in
great numbers. It is Without doubt an important- parasite in the con-
trol of the turnip louse over the State. This parasite has been very
efficient in the control of the “green bug,” which has been found in
many of the sections mentioned above. The following descriptions are
taken from Maryland Bulletin No. 152, by Mr. A. B. Gahan:

Fig. 6—Lysiph{ebus testaceipes Cress., a parasite of the turnip louse.
Adult female and antenna of male, greatly enlarged. (From Webster.)

Lysiphlebus testaoeipes Cress; Aphidvlus testaceipes Cress; L. itrit/ici Ashm.

Female: Length about 2 mm. Head distinctly transverse, as wide as the
thorax at the tegulae, black, smooth and shining; the temples convex; not
broad; clypeus transverse, about twice as wide as long; mouth parts usually
yellowish, occasionally fuscous. Antennae 11-13-jointerd, (usually with 13 joints)
black or brown-black, the joints approximately equal in length throughout and
about twice as lo-ng as thick; the two apical joints are sometimes connate,
forming a single joint much larger than the others. Thorax black, smooth and
shining, the parapsidal furrows absent or o-nly faintly indicated at the anterior
angles of the mes-onotum, the propodium flattened or depressed posteriorly, the
spiracles visible but not prominent. Wings hyaline, veins and stigma brown;
the stub of cubitus varies somewhat in length but is never longer than the
crossvein, usually shorter; the cubital crossvein is often indistinct, lacking the
pigment, but can always be traced by a hyaline fo-ld. F-o-relegs including their
coxae yellow; middle and posterior ooxae, femorae, and tibiae, usually though
not always fuscous, often nearly clear yellow. Abdomen lalnceol-ate, compressed
at the apex, about one and a half times as long as the head and thorax, black
or brown-black, except the petiole which is usually yellow; the ovipositor
sheath black. ’ ‘ a

Male: Antannae 14-15-jointed; the joints slightly shorter than in the female. ,

Abdomen scarcely longer than the head and thorax, rounded at the apex. Mid-
dle and posterior legs usually fuscous, occasionally clear yell-ow. In other re-
spects the male is like the female. - ' .

54-. TEXAS AGRICULTURAL EXPERIMENT STATION.

To the list of host plants as given by Webster (l.c.) Aphis pseudo-
brassicae must be added.

The life history of this parasite, which is given in detail by Webster
(l.e.), is briefly reviewed here.

‘The females usually begin ovipositing within a few hours after they
emerge, even when the males are not present, and the eggs may hatch
parthenogenically. The manner of ovipositing is shown in Fig. '7,
though the attack is not always made in this way. Very seldom is
more than one egg deposited in a single louse, and the number of lice
which a. single parasite will “sting” varies greatly, being sometimes over
200. Lg/siphiebazs prefers to oviposit in those lice which are in the
second or third instars. Lice stung at these ages will mature and may
reproduce for two or three days. The length of the period from the
egg to the adult varies greatlv, the averages for August, September and
October being 15.9 days. The hosts of this parasite include several
genera. of Aphids which occur over most of the United States. Lysi-
phlebus can withstand severe cold, for in the North it may survive the

' winter in the mature larval stage within the host. The adults have been

kept alive for two weeks when the temperature was below freezing.

 

Fig. 7-—Lysiph!ebus tesiaceipes ovipositing in the body of a “green
bug.” Enlarged. (From Webster.)

Winds exeart a great influence on the spread of this parasite and the
parasitized lice in flying from field to field are a great factor in the
dispersion of LysiphZeb/zzs. This parasite is not active when the tem-
perature is much below 56° F., and for this reason is not present in
numbers as early in the spring as the lice are, which are active at a
temperature of 50° F. a

The parasites were not observed during the spring of 1915 in the
gardens around College. On June 1, 1915, in a field of spring rape,
which was heavily infested with lice, the parasites were found to be very
abundant. The work of the parasite here was certainly reducing the
number of lice.

PREDACFOTIS ENEMIES.

Of the natural factors of control the predaceous enemies are of very
considerable importance. For the past ttvo years during which the
turnip louse has been observed‘ these factors have exerted much influ-
ence in keeping the pest in check. The past year (September, 1914,
to September, 1915) the parasites were present only in the late spring,
and the natural check of the lice was due entirely to the presence of

Plate III——Ab0ve, empty skins of parasitized lice on cabbage from which the parasites
have emerged. (After Herrick, Cornell Bull. .) Below, larva and adult _0f Chrysopa or
Lacewing fly, a predaceous enemy of the turnip louse. (After Hunter, UIllV. Kans. Bull.

THE TURNIP LOUSE. 55

the predaceous enemies. The same condition_ existed this year in many
sections of the State Where the turnip louse is  serious pest. The
presence of the predaceous enemies d.oes not depend to such an extent
upon climatic conditions as does that of the parasites.

Lady Beetles.

Of. the predaceous enemies, the most important are the ladybird
beetles or coccinelids. These insects feed upon plant lice in both the
larval and adult stages. Observations and reports indicate that the
beetles are usually present in those parts of the State Where the lice
are a pest, but While present they seldom become abundant enough at
the right time to eradicate the lice. At Beaumont the beetles appar-
ently hold the lice in check and at Brownsville the latter are seldom
a pest, probably due to the presence of the beetles in great numbers.
At Henrietta, during the fall of 19111, the beetles Were the only factor
of natural control present and the louse infestation Was not serious.
The beetles are present in other sections of the State but never check
the pest to such an extent.

It is hard to fullv appreciate What a factor of natural control the
ladybird beetles are until a. study is made of their ability to destroy
lice. The eggs are always laid close to the lice so the larvae of the
beetles Will have an abundance of food near at hand When they hatch.
When full-grown these larvae attach themselves to a. leaf on which are
plenty of lice in order that the adult When it emerges Will not have to
seek long for food.

There are three species of ladybird beetles present in the gardens at
College Station. They are Flippodamzia- convergens Guer. ; M egilla ma-
culaita. DeG, and Ooccinellrt mundai Say. The first tWo named species
are about equally abundant and the last is present only in limited
numbers.

Sanborn* found in 1906 at College Station that H. convergens adults
collected in April deposited 556 eggs over a period of 34 days, a daily
average of 16 eggs. These eggs hatched in 2 days, the» larval period
was 11 days, the pupil period Was 41- days, making a total of 1'7 days
from the deposition of the egg to the emergence of the adult. He
found that a single larva may eat 396 lice during its life of 11 days,
an average of 36 lice per day.

Webster (l.c.) records cases of the adult of H. convert/ens eating 30
lice per day. Hunter: states that by actual count these insects Will
devour from 30 to 100 lice in a dav. Miss Palmer} states that the
adults of this species ate daily from 36 to 180 lice.

In the Work ivith N. mandate, Sanliorn found that during August
one adult deposited 2-19 eggs over a period of 24 days, an average of. 9
eggs per day. During September and October, only 15'?’ eggs Were de-
posited in 4'7 (lays, an average of only 3 eggs per dav. During August
the eigg stage Was 2 days, the larval period Was 9 days and the pupal

 

*Bulletin No. 98, Oklahoma Experiment Station.
ttBulletin, Univ. Kan, Vol. IX, No. 2.
TAnn. Ento. Soc. Am., VII. 3, p. 215.

56 TEXAS AGRICULTURAL EXPERIMENT STATIQN.

period 5 days, making a._total of 16 days from the deposition of the
egg to the emergence of the adult. He found that a single larva ate
an average of 32 lice per day. The consumption of food by the adult
depends much upon the season. In August the average numb-er of lice-
eaten daily was 63, in September r16, in October 33 and in November 15.

The experiments conducted by Sanborn with (.7. wtunda. Were'made in
June and .luly. He found that a. female may lay 4118 eggs o-ver a
pe-riod of 36 days, an average of 12 eggs per day. The egg stage of
this species Was 2 days, the larval stage 9 days and the pupal stage 2‘
days, a total of 13 days from the deposition of the egg to the emergence
of the adult. The larva of this species ate 553 lice in a period of 9
days, an average of 61 lice per day. The adults ate 706 lice during
their life.

Fig. 8-—The convergent lady-beetle (Hippodamia convergens), an
enemy of the turnip louse. a, adult; b, pupa; c, larva. Enlarged.
(After Chittenden from Bureau of Ento. Bull. No. 100.)

Under ordinary conditions the beetles will not travel far from their.

place of emergence, but if food becomes scarce they may fly some dis-
tance in search of better feeding. On November 4, 1913, most of the
beetles were feeding upon lice ‘on radishes which were heavily infested.
These plants had not been sprayed 0r fumigated, and it was evident

that all of the beetles in the garden had gathered on them Where there.

was an abundance of lice. This condition was again evident on No-
vember 10.

The adult beetles are not injured With the sprays which have been
used in the spraying experiments against the lice. After the applica-
tion of each material an examination was made and no dead beetles
could be found. Many larvae Were observed unharmed after the ap-
plications of the soap solutions. On September 8, 1914, one larva was
found dead Where Black Leaf-AG had been used. While fumigating on
November 12, 1913, many beetles were present upon the plants. After
the fumigation was completed these beetles ran about in a very excited
manner, but did not seem to be injured in any way. l

The very hard rains which occurred during the latter p-art of No-
vember and the early part of December, 1913, apparently killed most of
the beetles which were then present in the fields. It was not until
January '7, 1914, that a. single specimen of H, con-vergens was observed.
During January, February and March of 1914- the beetles were present

THE TURNIP LoUsE. 57

in limited numbers but were a source of much trouble, as they Worked
upon the outdoor host plants and nearly cut off the supply of lice-. The
beetles would probably have eradicated the lice if measures had not been
taken to prevent it. On March 10, 1914, H. convergent?" Was the only
species present, but by March 31, M. wzaculaifa, Was present in limited
numbers. On April 4 quite a few larvae Were observed Working on
the lice upon the turnips; these larvae were one-third to two-thirds
grown. The first pupa Was taken on April 10, 1914, and many larvae
were observe-d on the same day that Were almost full grown. From
April 24 to .28 M. macuZat/ia xvas the most common species present
in the fields, but two days later H. conzrergens Was again most common.
Pairs of M. muiwz/ztlrtta. Were observed m coitu on April 25 and of H.

Fig. 9——The spotted lady-beetle (Megilla maculata), an enemy of
the turnip louse. a, larva; b, empty pupa skin; c, adult. E.nlarged.
(After Chittenden from Bureau Ento. Bull. N0. 110.)

con/vergens on April 29. Through the month of May, H. conivergens
Was the most abundant species on the turnips. There Were only a few
M. Wldfllldid- present during this time, and not a single U. munda. Was
observed.

By September 18, 1914, the ladybird beetles Were present in num-
bers upon the turnips Which Were infested With lice about September
5. The beetles Were very ‘abundant by September 29, mostly H.
conoergens. One pair of this species Was observed in coitu. on Sep-tem-
ber 26 and another pair on the 29. By October.12, M. ma-culaita
Was quite abundant and H. con/uergens Was present only in limited
numbers. On Octo-ber 29, larvae, pupae and adults of H. convergens
Were observed on turnips. On November 3, 1914, the adults of this
species Were found in numbers at Amarillo, Texas. On the following
day at Wichita Falls the adults of this species Were observed in num-
bers on turnips Which had just recently become infested With the lice.
On November 6, at Henrietta, this species Was quite common in the
gardens Which Were louse-infested. At the latter place, H. convergens
Was the only species ‘xvhich had been present during the entire season.
At Brownsville in January, 1915, the beetles Were present in the fields
in large numbers. Here H. convergens was the most common species

58 TEXAS AGRICULTURAL EXPERIMENT STATION.

at that time, but during some other periods M. ma-culaita is the most
abundant.

In the College garden some adult M. maculata Were observed on
radishes on February 3. Coccinelids Were not observed again until
March 12. At that time most of those in the garden were H. 00n-
vergens. A few larvae were also observed on this date. One pair of
this species were observed in coitu on this date. During the last half
of March the coccinelids increased rapidly in the gardens. H. 00n-
vergen-s was alwauvs most numerous, though the proportion of M.
muciulata increased. During this time copulation among the beetles
was frequently observed, but no eggs were found until the. middle of
April. During the early part of April C. miurzida was found in limited
numbers. On April 15 .711. wiaculata was the most abundant species
in the gardens. Eggs. of all species were observed in numbers on April
20. The beetles increased until the middle of May, when the lice
were gradually disappiearing from the fields.

Sy/rjflaial Flies.

In many places where the turnip lice are present, and especially
Where they are abundant, the syrphid flies are to be found. These in-
sects are beautiful two-Winged flies with prominent gold bands across

Fig. 10—Syrphus americanus, the larva feeds upon turnip lice. a, female fly; b, second
abdominal segment of male. Enlarged. (From Webster.)

the abdomen. They have the peculiarity of poising in the air over the
plants which are infested with lice. This has caused them to be called
“hover flies”. The syrrphid flies resemble the honey bee somewhat but
are readily distinguished from them by their peculiarity of remaining
still in the air. The eggs of this insect are usually placed singly on
the under sides of the leaves near the lice. The larvae are always

THE TURNIP LoUsE. 59

found where the food is most abundant. These larvae are slug-like
and dirty gray in color. This is the only sta.ge of the insect which
preys upon the plant lice. The few observations which have been made
upon this insect indicate that it has a Wonderful appetite for lice.

During the season of 1913, the first syrphid fly was observed on N o-
vember 21. This proved to be Syrpiz/zzs americavtus, Wied. It is quite
probable that they had been present some time previous but had not
been detected. Syrphid larvae were observed on December 19, 1913,
upon turnips in cages, which were being used for host plants. No
stage of the insect was observed again during the winter, and it is not
known how that season of the year is passed. Larvae Were again ob-
served on March 31, 1914-, a.t which tirnethe lice were not very abund-
ant on turnips. The flies were first observed in the fall of 1914 on
September 25. A few days later when some spraying experiments
Were being conducted some larvae were seen.‘ The adults were quite
numerous until October 10, when the food supply was cut oif by a
more thorough application of spray materials.

On April 6, 1915, material was received from Brownsville which con-
tained all stages of the oblique syrphid, Allograpta, obliqua Say. A
larva of this species was observed at College on April 15. The
adults of both species of syrphids were unusually abundant during the
latter half of April.

Lace-l/Ving Flies.

The lace-wing fly, or Chrysopa, is often present in localities where
the turnip louse is abundant. Their presence is indicated by small
white eggs on fine silk-like stalks on the under sides of the leaves. The
adults or flies are light green in color, the ivings are very large and
have many lines running across them. The flight of the insects seems
to be very ditficult, as though they could only flutter along. The young
larvae run about freely on the leaves of the plants in search of food.
The plant lice are taken up by the larvae in their strong jaws and the
juices sucked out. Webster (_l.c.) states that one species which is very
common in the Southwest hihcrnates over winter in the adult stage and
begins depositing eggs when the first warm spells occur in the spring.

Eggs 0f Cll1ry'sopa were first observed in the spring of 1915 on April
6. During the first half of this month the eggs were observed fre-
quently. The adults were often observed but never were abundant.

FUNGUS DISEASE.

This ‘factor in the natural control of Aphis pceuidobrassicaie is very
interesting because of its sudden appearance and its effectiveness in
eradicating the pest. The fungus which was so prevalent in our work
was undoubtedly Elmpusa spp. The groxvth and reproduction of Em-
pusa. as given by Tha.xter* are briefly given here.

The infection is started with a coni.dial spore coming in contact with
the skin of the louse. 'I‘he entrance  made by means of hyphae of

*Mem. Bos. ‘Soc. Nat. Hist, IV, 6, p. 139.

60 TExAs AGRICULTURAL EXPERIMENT STATION.

germination at some point where the skin is tender. When inside the
body these hvphae develop very rapidly, at the expense of the soft body
tissues. The growth of these hyphae may be by the formation of hyphal
bodies which are reproduced by budding. Sometimes the hyphae branch
in all directions forming mycelium within the body of the host. When
the fungus has about completed its growth, at wvhich time the louse is
about to die, hyphal bodies are formed. ,At this time, if climatic con-
ditions are favorable, the fungus will complete its development, but, if
conditions are not favorable, a “chlamydospore” is formed,-which en-
closes the contents of the hyphal bodies with a thick wall. The fungus
may remain dormant in this stage for several Weeks, if necessary, until
proper conditions for growth present themselves. If the fungus has
completed its growth and is ready for reproduction the hyphal bodies or
the chlamydospores germinate rapidly. The hyphae from these grow
very rapidly; one or more may come from a single hyphal body. These
hyp-hae may grow directly to the outside or they may branch and each
branch grow outward to become a “conidiophore.” In Empusa. aphi-
dius, the hyphal bodies branch in all directions and in great numbers,
to such an extent that the body of the louse is very much distended.

The germination of these hyphal bodies may result in the formation
of sexual or asexual (resting) spores, or “conidiospores.” .When' the
latter is the result, the hyrpliae grow’ outxvartl rapidly, break through
the skin of the louse and form a spongy mass on the outside. When
outside, these hyphae branch and the ends of each grow to the same
height. The terminal portion of the conidiophore is usually swollen
somewhat and is called the “basidium.” At the tip of the basidium is
a bud which grows from the rest and becomes the “conidium” after the
separating wall has grown between. The conidium thus formed within
the apex of the basidium absorbs water, expands and breaks through the
wall surrounding it. As a result of this the spore is thrown out, some-
times for a considerable distance.

If these conidia, when liberated, come in contact with proper en-
vironment they send out hyphae of germination, which enter the body
of the host as was first described. Such germination usually takes place
soon after the conidia are discharged. If the conidia do not fall in
suitable surroundings, they will form a secondary conidia after the
same fashion. This serves as a means of further spread when the pri-
mary spore has not fallen well. The primary spore produces a hypha
which grows upvsrard, becomes swollen at the tip into the basidium in
which develops a conidium similar to its origin and is discharged in
the usual manner. This process may be repeated until the substance is
exhausted, if the spore does not find suitable environment for growth.

. If the germination of the hyphal bodies does not result in the forma-
tion of the conidia as just described, resting spores wrill be formed.
This resting condition may be accomplished by a non-sexual process re-
sulting in “azygospores” or by a sexual process resulting in “zygo-
spores.” The azygospores may be formed in several ways, by the con-
tents of the hyphal bodv being converted directly into the spores, or the
germination hyphae ending in the spore. When zygospores are formed
the process may vary considerably. The simplest method is for the

germinating hyphae to send out lateral shoots which meet midway be-

THE TURNIP LoUsE. 61

tween the hlyphae. A bud then grows rapidly, absorbing the contents
0f the conjugating cells. Sometimes this conjugation takes place on
the outside of the host. The causes of the formation of the resting
spores cannot be satisfactorily explained.

The fungous disease was first observed during the fall of 1913, on
November 12. At this time some radish leaves Were collected for
examination as to the condition of the li.ce upon them. The lice were
found dead; some were dry and bronze-colored, while others were punky
and orange-colored. These dead lice were mostly pupae, some imma-
ture ap-terous forms and a few winged lice. Just a week later the (lis-
ease was found upon lice on ‘(F11lSt€l.I‘(l where fully 30 per cent. of those
lice had recently died. Most of the dead lice were immature apterous
forms, though there were many pupae and some winged lice. The
fungus was also found on the lice feeding upon turnips, and it soon
spread to all the gardens in the vicinity. The spread of the fungus
threatened to exterminate the lice on some of the host plants, such as
beans, lettuce and mustard. In two weeks from the time the fungus
was first. observed the lice were almost entirely destroyed.

On November 26 a very hard rain occurred, a.nd this apparently
checked the growth and spread of the fungus to such an extent that
dead lice were seldom seen on the plants. The rains which occurred
in the following two weeks killed nearly every louse on the plants, and
the disease disappeared. '

The fungus was next taken on lice in the fields on December 19.
In some outdoor observation cages the lice were found to be dying
rapidly from the disease on January '7, 1914:. Two weeks before this
it was cold but apparently not cold enough to p-revent the fungus from

u

developing. The dead lice found at this time were mostly apterous and

only a few winged forms. Within the next week the lice were almost
entirely killed in these cages.  they were wanted for experimental
work, an effort was made to stamp out the disease. All of those» leaves
which had dead lice upon them were cut from the plants and de-
stroyed. After repeating this operation several times the disease was
apparently checked, and then all of the healthy lice were transferred
to new plants in new cages. About a month later the disease was
found again in the outdoor cages. This was shortly after the low tem-
perature of 17° F, and a week during which low temperatures pre-
vailed. During the last half of February it was quite cold and the
fungus did not spread rapidly. lit was not until March 1O that the
disease was found to be spreading, but within two weeks most of the
lice in the cages had died from i.t.

On March 94. material was collected to start some experiments in
spraying louse-infested plants to disseminate the disease. Lice which
had died from the disease were scraped from the leaves .taken from
badly infested plants. These were put into rain water and thoroughly
shaken to break up the masses of fungus. The application of this mix-
ture was made with a. De Vilbiss atomizer. The plants were well cov-
ered with the spray, which was so applied that it would settle onto the
plants as a mist and not as a driving spray, which would knock the
lice oflf the leaves. It is not possible to say just how successful these
experiments were, as it was not possible to properly isolate the check

62 TEXAS AGRICULTURAL EXPERIMENT STATION.

plants from natural infection. During the time that these experiments
were made the disease W35 very prevalent i11 the fields adjoining. Many
lice died 0n all the sprayed plants, but not enough to say that the
measures would be practical for the control of the pest. A very large
per cent. of the lice which died were pupae. Most of the dead apterous
lice were immature forms. Those lice which had contracted the dis-
ease could be distinguished by the straw color of the body, which became
swollen just before death. When the lice die their bodies are much dis-
tended, orange in color and velvety in appearance.

The disease was found to be Widespread in the fields on March 30,
1914. At this time but few lice could be found which did not show
signs of having the disease. Most of the pupae present upon the plants
were dead and the apterous lice of all ages were dying rapidly. In
many gardens the disease had killed the lice out entirely. At that time
of the year there was considerable dew upon the plants each morning,
which was doubtless favorable to the reproduction of the fungus. Very
often the dead bodies of the lice would be found in a small bead of dew.
Under such conditions the spores of the fungus should develop rapidly.

The disease was prevalent in the fields throughout the month of
April. By the first of May fully 25 per cent. of the lice on the tur-
nips were dead from the fungus. By the end of another week 40 per
cent. of the lice were dead, and in two weeks more at least_75 per cent.
were dead. From that time on the lice gradually disappeared.

It is very evident that the fungus is a destructive enemy of the tur-
nip louse, and that if it could be controlled it would be a big factor
in eradicating the pest. The disease was very persistent throughout
the fall of 1913 and the spring of 1914. During the fall of 1914 not
a. single louse was observed at College Station which had_died from the
disease. This is probably because the climatic conditions of the two
seasons were so different. It does not seem possible to propagate the
disease when the conditions are unfavorable.

In January, 1915, when at Brownsville, the writer was told that the
lice were being held in check by lady beetles. Examination of the lice
0n the plants in the infested fields revealed the fact that the fungous
disease was present and was working effectively. On the plants lice
could be found which were about to succumb, as well as others that had
but recently died. The raunkyrlwodies of the lice which had been dead
for some time were abundant. The disease was spreading rapidly among
the lice on the turnips. As the infestation of. lice was light, most of
those present were apterous. The lice which were dying were almost
mature.

ARTIFICIAL CONTROL.
SEASON 1913.

_ As the study of the turnip louse was started rather late in the season,
the experiments with control measures were not conducted under the
best conditions. Naturally this work was of a. preliminary nature, but
it was expected that some results might be obtained which would serve
as a basis for future work along this line. When the work was started,
all of the turnips were heavily infested with lice and had been for
some time. '

THE TURNIP LOUSE. 63 l

SPRAYING.

Spraying was first investigated as a means of control for this pest.
This Work was started 0n a small scale, as the efforts were not »well
enough organized to undertake extensive experiments. The results of
the Work were not all that was expected of it. The difficulty was not
in getting material to kill the lice but in getting the material onto the
lice. Black Iieaf-40, kerosene emulsion and whale-oil soap were selectea
for the trial Work. The results of these experiments are briefly given
here.

Turnips.

(Black Leaf-40.)

A small area of broadcasted turnips were sprayed on October 25th
with a solution of this material. The spray was made according to
the directions on the package, five ounces of the black leaf-40 and one
pound of whale-oil soap to thirty gallons of water. The application
was made with a. bucket spray pump, equipped with a long hose, an
extension rod, a 45° elbow and an agle type nozzle. The material
was applied early in the morning while the dew was still on the leaves.
Care was taken to cover all of the leaves so as to hit all of the lice.
The plants were only four inches high, but the ground was covered by
the foliage.

Immediately after the app-lication was completed an examination was
made, and no living lice could be found. There was a slight odor of
tobacco present on the leaves. Two days later another examination was
made, and no living lice were found upon the sprayed plants, but on
the check plants the infestation was increasing rapidly. The tobacco
odor had entirely left the leaves.

(Kerosene Emulsion.)

A patch of turnips, similar to the above, was sprayed with kerosene
emulsion on October 30. A proprietary stock solution was diluted ac-
cording to directions on the container: to make a 5 per cent. solution
of oil. This stock solution was well made, as no free oil had separated
out. The day was cool and the application was made late in the after-
noon. The outfit was the same as was used for applying the black
leaf-40. While the application was being made there was a decided
odor of kerosene, but none of the leaves showed signs of burning. Im-
mediately after the application no living lice could be found on the
plants. Two days later an examination showed that no lice were on
these turnips. The odor of kerosene was gone and there were no burned
leaves.

Another test of kerosene emulsion on turnips was made where the
plants were in rows; the infestation on these plants was heavy. For
this application home-made stock solution was used. It was made by
the common formula of one-half pound of soap, one gallon of water and
two gallons of kerosene. The usual care was taken in making the stock
solution, but free oil separated out after it stood awhile. The applica-
tion was made with a. knapsack sprayer, which was placed on the- ground
so that ‘the nozzle could be directed toward the under sides of the leaves.

64 TEXAS AGRICULTURAL EXPERIMENT STATION.

The application was tedious and unsatisfactory, as many of the leaves
were not touched with any of the material. As soon as the material
dried, many leaves showed evidence of burning and before the spraying
was finished the patch looked as though a fire had gone over it. Two
days later all of the turnips were dead. from the severe burning of this
material.

The result of this spraying is evidence that kerosene emulsion is not
always properly made by ordinary help and that such help will not take
the proper care to apply a. contact insecticide. It is clear that these
two factors play an important part in the control of the lice.

(No. 6 Soap.)

On October 30 a. patch of turnips which were planted in rows was
sprayed with a solution of Good’s Caustic Potash Tobacco Fish Oil
Soap No. 6. The solution was made as directed, one ounce of soap to
one gallon of water. {The application was made with the bucket pump,
previously described. The leaves of the plants were large and the foliage
was dense, which made it difficult to apply the material eifectively; An
examination made after the spraying was completed showed that all of
the lice had not been hit and the results could not be satisfactory. Two

. days later the lice were found well scattered over the plants.

As this application was not effective, another was made five days
later. The same material and outfit were used again. More time and
material were used in an effort to make a careful application. The eX-
amination made immediately after the spraying showed that some of
the lice had not been hit this time. A week later the turnips were ex-
amined. On the check rows the infestation was very heavy; on those
plants which were sprayed only once the lice were quite abundant.
There were but few lice on those plants which had been sprayed twice.
The second application following closely after the first proved to be a
decided check on the lice.

Spraying will not entirely eradicate the lice when made under such
conditions as these trials were conducted. ’I.‘he plants were too large
and the infestation was too heavy when the spraying was started. All
of the materials tried gave good results when properly applied. Tur-
znips sown in rows are much easier to -spra_v than those sown broadcast.

The cost of the concentrated solution of black leaf-4t0 seems very
high, but when properly diluted the spray is not expensive. The ma-
terial is easy to apply, it spreads well on the leaves and does not in—
jure them. However, this material is more expensive than the other
two. Kerosene emulsion is a good material to use, since the ingredients
can be purchased any place and it can be made at home. But if it is
not properly mzlde more harm than good will be done by using it. The
material spreads on the plants nieelv and the odor does not persist long.
On account of the danger of making a poor emulsion, this material is
not to be recommended ahead of the other two materials. The No. 6
soap is a soft soap and dissolves readily in a small quantity of boiling
water. This concentrate can easily be taken from place to place and
the dilution made then as needed. The spray spreads easily on the
leaves and dries oif quickly. The odor of fish does not persist long.
The cost is low if the soap is purchased in quantity.

Plate IV—_—A bucket spray pump properly equipped for spraying against the turnip
louse. (Orlginal).

THE TURNIP LoUsE. , 65

Cabbage.

The lice did not infest the cabbage this season until November 12th.

The spraying was not started until five days later, when the infestation
was Well scattered over the patch. One-half acre of cabbage was used for
these experiments. The outfit used was a. hand-power pump equipped
with two leads of those, each having a four-foot extension rod, a 45°
elbow and an angle type spray nozzle. On the day the application was
made there was considerable Wind, which interfered with the Work.

(Black Leaf-40.)

Thisfsolution was made of S ounces of the black leaf-liO and 2 pounds
of hard whale-oil soap to 50 gallons of water. To this Was added. 3
pounds of rosin sticker soap, so that the material would spread evenly
over the cabbage leaves. As the day Was cloudy, the material did not
evaporate quickly, but no ill effects from this were apparent. The ample
force supplied by the pump Was a decided advantage, as it Was possible
to drive the spray into the unfolding leaves Where the lice Were ordi-
narily protected. The examination made immediately after the appli-
cation was completed showed that all of the lice had been killed. Dur-
ing the following Week examinations did not reveal any lice up-on the

lants.
p (No. 6 Soap.)

-An adjoining patch of calfloage was sprayed with this material on
the same day as the above. The solution was made of 1 ounce of
soap to 1 gallon of water, and the rosin sticker soap was added; at
the rate of 3 pounds to 5O gallons of water. This material spread nicely
on the leaves and killed every louse present. The addition of the
sticker soap to these stilutions made the cost high, but it is likely that
further investigation will show that the sticker soap will partly replace
the Whale-oil soap in the formulae.

FUMIGATION EXPERIh-IENTS.

The spraying experiments during the early part of the season did
not give entirely satisfactory results. It did not seem possible to apply
the material so that it would be efficient and at the same time keep
down the cost of materials and application. Fumigation was next con-
sidered in hopes of finding a cheaper and more efficient means of eon-
trol of the louse. It was evident that it would not be practical to
fumigate turnips which had been broadcasted. The best means of fumi-
gatiug turnips apparently was to build a small portable fumigator, sim-
ple in construction and low in cost. The following fumigator seemed
to meet the requirements: The frame was made of 1 x 2 and 10 feet
long, with a brace of 1 x 2 put in the middle; the ends were 14 X 18
inches, made solid with ship lap; this frame was covered with muslin
of the heaviest grade that could be purchased. This cloth was 36 inches
wide and was put on the frame beginning at one edge of the top, going
across it and down the side. This allowed a four-inch flap, on which
dirt could be placed. The other side was covered with a half strip,

66 TEXAS AGRICULTURAL EXPERIMENT STATION.

which also allowed for a flap. The cloth was oiled to make it gas-proof.

i The cost of the material for this fumigator was 28 cents.

Laboratory experiments were conducted to determine the materials
which were best suited for use in the fumigator, and the time required
for each to become exhausted. Unsatisfactory results were obtained
from the use of tobacco papers, they seemed to smother out in the
small confined space. Tobacco dust would not burn in the small space,
even when ignited with kerosene. Tobacco stems gave satisfactory re-
sults when properly used. Tied in compact bunches, they burned nicely
after being lighted i.n the open. They could be easily lighted by pour-
ing a teaspoonful of kerosene on one end of the bundle. The bunches
burned best in the fumigator when placed in an upright position with
the burning end up.

Radish es.

The first fumigation experiments were made on November 10.-

The day was clear but cool. The radishes were large, the foliage
was very- dense and the infestation was extremely heavy. The charge of
stems was placed in the center of the fumigato-r. The first charge of
stems of one ounce was confined for twenty minutes. The lice were

not even stunnetl. by this fumigation. The second charge of 2 ounces

was burned for twenty minutes, and it was estimated that 25 per cent.
of the lice xvere killed. Two ounces of stems were used again, but

burned for thirty minutes this time. As a result of this long exposure '

to the fumes of 6O per cent. of the lice were dead and upon the ground.
The next charge was 3 ounces of stems, and they were b-urned for thirty
minutes. Fully 95 per cent. of the lice were on the ground under the
plants; about 8 per cent. of these were not killed but only partly over-
come by the fumes.

On November 12 the fumigation experiments with radishes were
continued. The day was cool and cloudy with a strong wind blowing.
At times this wind was too hard for satisfactory results. The stems
were placed in one end of the fumigator, as the wind seemed to push
the smoke to the opposite end. i

The plants were small and scattered on the ground; the infestation
was heavy. The first charge was 3 ounces of. stems, and these were
burned for thirty minutes. The result of this was that 8O per cent.
of the lice were found dead upon the ground. About 5 per cent. more
were crawling about on the ground but did ‘not seem to be injured by
the treatment. The second charge was 3 ounces of stems burned for
twenty-five minutes. Fully 90 per cent. of the lice were found upon
the ground after this fumigation. Of these, 5 per cent. were not en-
tirely overcome and would survive. The next charge was 3 ounces of
stems, which were burned for thirty-five minutes. This killed 95 per
cent of the lice and more were on the ground but were not entirely
overcome by the fumes. The next test was under the same conditions,
but 98 per cent. of the lice were found upon the ground.

Soon after the fumigations the foliage showed severe burning; some
of the plants were entirely killed. This burning was more severe on
the old leaves near the top of the fumigator. lt was more severe and
shoived. up quicker when the fumigation was prolonged. Those plants

THE TURNIP LOUSE. 67

Where the gharge was small and the exposure short did not show burn-
ing until the folloxving day. The burning seemed to be more severe on
those plants which had dew upon them when fumigated.

Turnips.

These plants were not as heavily infested as the radishes, but the
foliage was much denser. The first charge of stems Was 2 ounces and
they were burned for thirty minutes. This fumigation killed '70 per
cent. of the lice. The second charge was 2 ounces of stems, but these
were burned for thirty-five minutes. Only '70 per cent. of the lice were
killed this time. The additional time of confining the gas did not im-
prove the results. Another charge of 2% ounces of stems was burned
for thirty-five minutes. This killed 90 per cent. of the lice, but the
burning of the foliage was more decided. The turnips did not seem

to be as susceptible to burning as the radishes. Those lea.ves which i

touched the fumigator at any place seemed to be most severely injured.
illustard.

Not many trials were made with fumigating this plant, as the leaves
burned so badly. With the minimum charge and exposure most of the
leaves were seared, and the plants soon died.

The result of the fumigation experiments were not all that had been
expected. The burning of the leaves was such that it would not be
considered practical. The cost of the materials was about the same as
for spraying. The cost of application was the same for both, but the
cost of equipment was less for fumigation.

SEASON 1914.

This ‘year it was possible to ascertain the beginning of the infesta.-
tion of the lice in the garden. The spraying experiments were planned
to start before the plants were large and the infestation was heavy. It
was evident from the work of the previous year that spraying would
hardly eradicate the lice after they were well established on large plants.
Spraying as a- control measure xvas undertaken again this year because
the fumigation experiments of the previous year gave unsatisfactory
results. The spraying of last year was too expensive to be practical on
a large scale, so the aim in the work this year was to develop a cheap
and efficient spray. lliore materials were tested and the work was con-
ducted on a much more extensive scale.

SPRAYING.

The experiments were made in the vegetable garden of the Horticul-
tural Department of the College. There were two plats, one consisting
of 2 rows of radishes, 2 rows of mustard and 2 rows of turnips; the
other of 5 rows of turnips. The rows were 400 yards long.

68 Texas AGRICULTURAL EXPERIMENT STATION.

Radish es.
(Black Leaf-ALO.)

This solution was made of 12 ounces of the concentrate and 4 pounds
of whale-oil soap to 100 gallons of water. The outfit was a barrel pump
supplied with two leads of hose, each with a four-foot extension rod, a
45° elbow, and an angle type nozzle. The material spread on the leaves
nicely and was effective in so far as the application was perfect. An
odor of tobacco couldb-e detected for a few hours after the material
was ap-plied. The leaves dried quickly after the application. With this
outfit the application was very slow and unsatisfactory. The pump was
not in good condition and would not properly supply the two leads of
hose. It required a crew of 3 men two hours to apply the material to
1000 feet of plants. It is a great saving in time to use a good pump
an.d much easier to make an effective application. . With considerable
force the leaves of the plants are raised and the spray can be put onto
the lice with little effort.

' Three days after this application an examination was made, and many
lice were found on these plants. -

A second application xvzis made just a wreck after the first. This
time the outfit was a hand-power pump equipped with two-leads of hose,
each having a four-foot extension rod, a 45° angle Y and two angle type
nozzles. The pressure was maintained at '75 pounds. The immediate
results of the application were satisfactory, as apparently all of the lice
had been killed. A barrel of the spray material cost 6'7 cents. Five
hundred.‘ andisixty-four feet of plants were covered in twenty minutes
by the crew of 3 men.

( Sulfur.)

This material has been used some as a. contact insecticide, both as a
liquid and a. dry spray. Russell (Jr. Econ. Ent, I, 6,p. 3'78) used it
with much success against the red spider on beans. The sulfur was
used at the rate of 1 ounce to 1 gallon of water. The sulfur was
mixed with a small quantity of hot water, which was kept almost boil~
ing for fifteen minutes. In. this way it was hoped to more completely

- separate the particles of sulfur. The application was made on the same

day as the above, under the same conditions and with the same outfit.
Much (lifficultyr was experienced in the application of this material, as
the small particles of sulfur would clog the intake pipe of the pump and
the nozzles were constantly stopped with sulfur. Later in the day it
was necessary to take the pump apart, and particles of sulfur were
found around all valve seats and the plunger. The pump did not work
well until carefully cleaned.

The immediate results of this material were far from satisfactory,
though the sulfur wras well spread over the leaves. Since sulfur can
only kill when it comes in contact but few lice were killed,. as only few
particles of sulfur actually hit them. Even those lice which were hit
with the sulfur did not apparently suffer any. Soon after the applica-
tion the film of water on the leaves collected in small globules, and the
particles of sulfur were drawn on the surface of. these drops of water.
Many lice which had sulfur on them were able to crawl about, as soon

Plate V—Ab0_ve, a barrel spray pump, with cart, showing one lead of hose and attach-
ments for sprai/ing against the turnip louse; _be10w, a hand power pump, with barrelsupply
tank, showing proper attachments for spraying against the turnip louse. (OriginaL)

THE TURNIP Lousn. 69

as they could get from under the water. Not a louse was killed by the
appplication of this material. A barrel of the spray cost 35 cents.
This amount covered 576 feet of plants and the time of application
was thirty-five minutes. '

(Lime Sulfur Solution.)

A commercial brand of lime sulfur testing 32° Baume Was diluted
1 to 50 parts of water. The application was made with the hand-power
pump described above. When first applied the material was spread
evenly over the leaves, which gave the foliage a yellowish appearance.
This thin film of liquid seemed to irritate the lice, and no doubt would
have killed them if the lice cov/Jd hcmuc been, confined in it. However,
in a short time this film contracted into small globules over the leaves
and the insects crawled off unharmed. The leaves did not dry quickly
and there was considerable residue left upon them. This residue did
not seem to affect the plants any; it merely left them unsightly for a
time.

(Soluble Sulfur Compound.)

This material is recommended for use in the same manner as the
commercial lime sulfur solution. It is a powder which is dissolved in
cold water at the rate of 1% pounds to 50 gallons of water (for plant
lice). The resulting liquid is yellowish in color, like the weak solu-
tion of commercial lime sulfur. ' The application of the spray was made
with the same hand-power pump. The action of the soluble lime sulfur
upon the leaves and on the lice was the same as the commercial lime
sulfur. Three days after the lime sulfur sprays were applied an exam-
ination was made. The lice were found to be as abundant upon the
sprayed plants as upon the check plants.

(Laundry Soap.)

For this purpose the “Clairette” brand of soap was used at the rate
of 1 pound of soap to 5 gallons of water. The soap‘ was shaved into
a small quantity of boiling water and after dissolved diluted to the re-
quired amount. The soap does not dissolve readily, even in boiling water,
and the results are not satisfactory if too small a quantity of water is
used. The hand-power pump above described was used to make the
application of this. material. It spread onto the leaves nicely and dried
off quickly, leaving no odor. It is very effective against the lice. This
formula makes the solution too soapy, and it was diluted for further"
work. For this work the barrel of material required 10 pounds or 20'
bars of soap, which cost '70 cents. The barrel of liquid was sprayed out‘
in twenty minutes, and covered 700 feet of plants. t‘

Two weeks later another test was made with this material, using 1
pound of soap to 7' gallons of water. The soap was dissolved in a
larger quantity of water, and much better results were obtained. At
the strength used the material was very effective against the lice. The
cost of a barrel of this solution was now as low as any material which
had been used.

'70 TEXAs AGRICULTURAL EXPERIMENT STATION.

(Fish Oil Emulsion.)

This material Was made by dissolving 1 pound of soap in 1 gallon
of Water, then adding 2 gallons of fish oil. This Was then agitated vio-
lently to make a perfect emulsion. The stock solution Was diluted to
contain 5 per cent. of oil. Upon standing some time there Was a tend-
ency for some of the oil to come to the surface, which indicated that
the emulsion Was not properly made. The application Was made With
the hand-power pump described above. This material spread on the
leaves nicely and soon dried. At first there Was a decided fish odor,
but this did not persist long. The material Was effective against the
lice. The immediate results Were satisfactory, but in three hours after
the application the plants showed. severe burning of the foliage. Most
every plant Was dead by the end of a Week-after the application Was
made. The cost of this material is too high to be practical; one bar-
rel cost $1.25.

(N0. 3 Soap.)

Good’s Caustic Potash Fish Oil Soap» No. 3 is a soft Whale-oil soap.
This makes a satisfactory material to use, as it dissolves readily in a
small quantity of Water. From that standpoint, it is superior to the
hard WlIEIlQ-Oll’ soaps. The formula used was 1 ounce of soap to 1 gal-
lon of Water. The hand-power pump Was used in making this appli-
cation. The material goes onto the leaves nicely and is very effective
against the lice. The cost of a barrel of this material is 25 cents. A
second trial was made with this material, and'the results were again
very satisfactory.

(lVhale-Qil Soap.)

This Was the hard soap. Which is the form usually on the market. It
Was used at the rate of 1 pound to '7 gallons of Water. The soap Was
shaved into boiling Water, but it did not dissolve readily. In this re-
spect, it is not as easy to useas the No. 3 soap. The spray goes onto
the leaves Well and is very effective against the lice. The leaves dry
quickly and the odor of fish does not persist long. The cost of a barrel
of this material Was 50 cents.

M us turd .

The materials Which have been discussed above Were used on mustard
plants, Which Were adjoining the radishes. ln general, they Were not
as effective against the lice upon this plant as they Were upon the
radishes. The leaves of the mustard are so curly that it is diificult to
force the spray into the small folds Where the lice are usually found.
The sulfur solution seemed to- collect on the leaves of mustard more
readily than on radishes. The lice Were hardly inconvenienced by the
application of thees materials. The mustard suffered much more from
the application of the fish oil; not a single plant lived in the area
sprayed by this Inaterial.

Turnips.

These same materials Were tested on the turnips, which Were also
beside the radishes. The results of these trials Were in every Way the

THE TURNIP LoUsE. '71

same as those 0n radishes. The condition of these plants was such that
more effective spraying could be done than on the radishes. The de-
posit of the sulfur materials was not so pronounced 0n the turnip leaves
as 0n the radish leaves. When the turnips dried they looked as though
they had been covered with lime.

1n addition to the above tests, plat No. 2 of turnips was sprayed
throughout the season with No. 6 soap only. This material had given
satisfactory results in previous trials, so it was our aim to try it under
actual control conditions. The first application was made on Septem-
ber 15 when the plants were six to eight inches high. At this time the
infestation was not heavy, though the lice were well scattered over the
patch. The usual formula of 1 ounce of soap to 1 gallon of water was
used. The hand-power outfit previously described was used to make
this application. It was estimated that 95 per cent. of the lice were
killed with this spray.

On September 22 a second application was made on the turnips.
This time the plants were 12 to 14 inches high, and almost covered the
ground. The same formula for the spray and the same outfit were
used. The first application was so effective and this one followed so

closely that there were not many lice present, and these were well scat-

tered over the patch. A barrel of spray covered 757 feet of plants and
was applied in twenty minutes. This application killed 95 per cent. of
"the lice.

A third application of this material was made two weeks later. The
same formula and the same spray outfit were used this time. The plants
then entirely covered the ground, which made it diflicult to apply the
material without extreme care. The infestation was light and well scat-
tered over the patch. Examinations made on several days following
‘did not show a single living-louse. This No. 6 soap certainly proved
very effective against the lice, and the proper times for the application
were indicated by these trials.

GENERAL REMARKs ON PLAT I.

At the time the first spraying was d.one on September 15 the
radishes were 6 to 8 inches high and heavily infested with lice. The
mustard was 4 to 6 inches high a.nd only lightly infested. The turnips
were 6 to 8 inches high and the infestation was light. The applica-
tion was not effective, due partly to the improper application of the
material and partly to the poor results of the materials used. The lice
were just as abundant in a. few days after the application was made as
they had been before.

When the second application was made on September 22 many of
the radishes were dead from the severe infestation. The lice were
abundant on all the plants. The radishes and mustard did not grow
much between the applications, but the turnips were quite large. Pow-
dered arsenate of lead was added to all. the material this time at the
rate of 21, pounds to 50 gallons of water. This was necessary, as the
grasshoppers were becoming very destructive in the garden.

The third application was not made until October 6, two Weeks
after the second one. It was considered best to wait this long, as the
=second application had been quite effective and it was cool during this

'72 TEXAS AGRICULTURAL EXPERIMENT STATION.

period, so that the reproduction was 10W. When the application was
made, it was evident that a mistake had been made in waiting so long.
The lice had increased materially and the plants had suffered from it.
The plants were very large, so that it was difficult to make an effective
application.

Under these conditions, it was considered advisable to cut the large
leaves from the turnips and destroy them. In this way many of the
lice were carried away from the plants and destroyed, and it was a sim-
ple matter to spray effectively the few small leaves which remained-
The infestation was quite severe on all the plants.

PRFJVEN'I‘IVE MEASURES.

In thecontrol of the turnip louse, as in the control of most every
insect pest, preventive measures are to be employed whenever possible.
With the turnip louse these measures do not assure as much relief as"
is often the case in combating insect pests. But it is true here also
that the actual control of the pest is made much easier when the pre--
ventive measures are employed. When the turnip louse becomes well

_ established in turnips and radishes, the complete eradication is very dif-s.

ficult and unsatisfactory. While the natural factors may check the pest"
in time, such relief usually comes too late to be of real service. Com-
plete control of the turnip louse can only be expected when all of the-

preventive measures have been used and judicious spraying has been:
. employed.

ROTATION.

'l‘his very important factor of insect control is not as effective with
the turnips louse as with many insect pests. It is, however, of suflicient
importance to be practiced as much as possible. It does seem that in-

-jury by the turnip louse can be reduced by planting the new crops of

the host plants as far as possible from where the old crops were grown.
It is seldom feasible to abandon a garden site entirely, but the plant--
ings of the host crops should be so planned that they will not come-
together at the same time in adjoining plats. In some cases where a»
succession of host plants (radishes and turnips) is employed, it would
be advisable to discontinue a planting or two of each. This -would
make a break in the line of food and probably cause the lice to seek
other gardens where such crops would be growing at that time. When-
ever it is possible to arrange the rotation, radish should not precede-
the fall crop of turnips, and at best such a. planting of radishes should
not be next to the fall turnips. Where an early fall crop of mustard
is grown, one should leave as much time as possible between the end
of that crop and the fall. turnip crop.

PLANTING.

It is the general opinion of gardeners that the early fall crop of
turnips suffer most from the attacks of the louse. In the same way
the early varieties of turnips seem to suffer more than the late varie-
ties. It is true that in some sections there is not much chance for a

THE TURNIP LOUSE. '73

choice in the time of planting fall turnips, but wherever possible the
planting of the main crop of fall turnips should be delayed for a time.

TRAP CROPS

Such crops are those planted on a small scale at such a time as t0
attract most of the insects to feed. These crops are destroyed at such
a. time as the insect infestation upon them is at its height; not later
than such a time as the main crop may prove attractive to the insects.
If not destroyed early enough the trap crops will fall short of their
duty, since they will serve as a breeding place for the insects until the
main crops are ready. The trap crop, if properly employed, may be
made to serve as a big factor in the control of the turnip louse; if not
properly employed, it will work against the possible reduction of loss
by the lice. For the trap crop, turnips may be used by planting a row
very early along one side of the proposed turnip patch. If such a plan
is not adapted to the locality’, radishes may be used in the same way.
In many localities,.mustard is the best. trap crop to use, but the lice
will not remain long upon the mustard after the turnips are of much
size.

DESTRUCTION OF FIRST COLONIES.

When the turnip louse is known to be a pest in a locality, it is ad—
visable to inspect the fall crops from time to time to detect, if possible,
the first colonies that start in the garden. Usually the lice Will be-
come established upon a few plants in a defined area; there may be
two or three such areas. The destruction of these colonies at the start
will do much to prevent further injury from the pest. It is necessary
to repeat this process, for the lice will continue to come into the field
for a~considerable period of time and establish the small colonies. If
a careful inspection is maintained and all colonies destroyed at the
start, the injury to the field as a whole will be small. It is so much
easier to eradicate the louse in small areas than to wait and attempt to‘
spray the entire field. In one section of the State these small areas of
infested plants are surrounded by a strip of crude oil, the plants cov-
ered with straw and burned. It is said that such treatment holds the
pest in check. Any of the spraying suggestions given below may be
used in the destruction of the first colonies of lice.

CLEAN CULTURE.

While we do not know that any of the common weeds about the gar-
den serve as food for the turnip louse, nevertheless, it is advisable at
all times to practice clean culture. It is not advisable to leave the
remnants of the old crop in the ground when the new crop is coming
on. Any of the fall crop of turnips and radishes should be pulled dur-
ing the winter, or at least some time before the spring crops may be
subject to attacks. It will not do to merely pull the crop and. leave it
on the ground, for most of the plants will be able to root enough to
stay in a growing condition and be food for the lice.

'74 TEXAS AGRICULTURAL EXPERIMENT STATION.

SPBAYING.

T0 employ the preventive measures here suggested will surely reduce
the possible injury by the turnip louse. However, it seems that the
pest will not be entirely eradicated by those measures alone. After all
of the above measures have been followed, the fall crop of turnips may
still be infested With the lied. When the lice are present in the fields,
spraying is the most satisfactory means of combating the pest.

MATERIALS.

The spraying experiments conducted show that the soaps are the most
satisfactory materials to use. All of the whale-oil soaps were very effec-
tive, but, as they are not alwayjs available over the State, the use of
laundry soap is advised. For this purpose a good grade of laundry
soap should be purchased. The “Clairette” brand Was used in the ex-
periments. The formula given, 1 pound of soap to *7 gallons of water,
is considered the best. The soap should be shaved into boiling water,
at the rate of about 1 p-ound of soap to 2 gallons of water. The soap
does not dissolve readily in any less water, and if the water is not boil-
ing the soap will dissolve very sloxvlyr. It is necessary to frequently
stir the shaved soap in the water to facilitate the dissolving. After the
soap is dissolved, dilute to make the above formula.

The materials used for the spraying against the turnip louse are
called “Contact Insecticides.” Such materials kill only when they come
in contact with or hit the insect. It can readily be seen that extreme
care must be used in the application of such materials in order that
they may b-e effective. Any louse which is not actually hit with some
of the spray is not harmed in any way by the application. When the
lice are known to be starting in a garden, preparations should be com-
pleted at once for the sprayring. Any delay in this matter is serious, as
the. lice will spread rapidly and the eradication is much more difficult.

‘Experience shows that it is almost impossible to hit and kill all of the

lice with one. application, especially by those people who have not had
much experience in such work. Even with extreme care in the appli-
cation of the material, some of the lice may remain upon the plants.
Also, in the early part of the season, the first application of the ma-
terial may be given before the migration of the lice has ceased. In this
way a field which has been freed of the lice may become reinfested and
make it necessary to spray again. A third application is usually neces-
sary to hold the pest in check. These three applications should be given
at intervals of seven to ten days; in some cases, it may be advisable to
wait longer between the second and third application, but it is not best
to wait too long. “Jlhe spraying should be started early, while the
plants are still. small, for the smaller the leaves the easier it is to spray
effectively. If the leaves of the plants are very large, most covering
the ground, before the last application is made, it is advisable to pull
most of the leaves, as for greens, and destroy them. In this way, many
of the lice will be killed and the application can be very effectively made
to the remaining leaves. That will allow a great saving in the amount
of spray material necessary to cover the plants and in the time neces-
sary to make the application.

THE TURNIP LoUsE. '7 5
APPARATUS.

For the application of any of the contact insecticides, it is necessary

to have a good spray pump. When spraying to eradicate the turnip»

louse, it is necessary to have an extra good pump and outfit. As the
lice feed almost entirely upon the under sides of the leaves, it is neces-
sary to- have some special accessories. With any pump, a fifteen-foot
lead of hose is necessary for use against the turnip louse. The equip-
ment for this purpose must include an extension rod; four feet length
is the best length. To properly direct the material onto» the under
sides of the leaves, it is Irecessary to use an “angle” type of spray noz-
zle, which must be attached to, the extension rod by means of a 60°
elbow. The secret of success in spraying against the turnip louse is
the use of the angle nozzle and the elbow. These accessories are neces-
sary to any equipment for such spraying. There are three classes of
spray pumps which may be used in this work. The class of pump
which it is necessary to buy depends upon the amount of work that has
to be done. Only a good outfit of any class should be purchased. A
good spray pump will give good service, but a poor outfit will never
give satisfaction.

The bucket pump, shown in Plate II, is an example of this class of
pumps. The photograph shows the pump with the proper accessories
for spraying against the turnip louse. Such a pump is quite limited
in its range of usefulness. It is adapted only for use in the home
garden, and is not large enough for the truck grower. The applica-
tion of material with such an outfit is too slow and expensive for one
who has much area to spray. If one is growing only a few turnips in
an infested district, it is necessary to have some kind of a spray outfit,
and a bucket pump will serve this purpose. Specifications and esti-
mated cost of such an outfit are here given:

Brass spray pump, with 1 angle nozzle . . . . . . . . . . . . . . . . . . . . . . . $3.25
Rubber hose, Et-inch, 3-ply, 15 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.50
One extension rod, 4 foot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
One brass 60 degree elbow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

$6.40

The barrel pump, shown in Plate III, above, is an example of this
class of spray pumps. The photograph shows the accessories for spray-
ing against the turnip louse. In this photograph the pump is fitted
with only one lead of hose. Hoxvever, a good pump of this class should
supply’ ample pressure for two leads of hose. Unless it will do this the
outfit is not good enough to buy. It happens that at times the pump
will not furnish good pressure to two leads of hose. Under such con-
ditions, it is best to use only one lead with good pressure. Two leads
of hose with poor pressure makes the application expensive and unsatis-
factory. The experiments proved that it is best to use as high pres-
sure as possible for all spraying work. It is not necessary to have the
cart shown in the photograph, as the pump can be hauled about the
field in a small wagon. A good barrel spray pump has a wide range
ol.’ usefulness. It is best adapted to the needs of the small truck gar-

76 TEXAS AGRICULTURAL EXPERIMENT STATION.

dener but may be used by the large growers. Very often it is advisable
for two or more growers to purchase can o-utfit together. This will ma-
terially reduce the individual cost on the start. Specifications and esti-
mated cost of a barrel sprayer adapted for the work against the turnip
louse are here given:

One barrel pump, with brass cylinder, one brass cut-out, two

leads of hose, el-inch, 5-ply, 15 feet, two angle nozzles . . . . . . . $18.00
Two brass 60 degree elbows . . . . . . . . . ., . . . . . . . . . . . . . . . . . . . . . .50
Two extension rods. ._. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
$19.30

The hand-power pump, shown in Plate III, below, is a specimen of
this class of spray pumps. This pump will supply ample pressure for
two leads of hose, each having two nozzles. With such an outfit as
here shown it is possible to spray turnips very effectively and economi-
cally. The cost of this outfit puts it beyond the reach of many truck
growers, but if one has many crops to spray it is the best outfit to
purchase. If two or more growers could go together for the purchase
of this outfit the first cost would not be prohibitive. Specifications and
estimated cost of such an outfit are here given: _

One hand-ploxver pump, .50-gallon barrel, mounted on sled, pres-
sure gauge, two 15-foot leads of 7-ply hose, {--inch, two exten-
sion rods 4.- feet, two brass angle Y’s, four angle nozzles . . . . . $35.00

It is possible to purchase a hand-power pump and accessories without
barrel and sled for $29.25.

SUMMARY.

A new species of plant louse, commonly called the turnip louse, and
not the cabbage louse, as wasformerly supposed, does the damage to
the fall turnips and winter truck. This damage is general over the entire
State of Texas. Not only do the truck regions suffer, but every home
garden is damaged by the turnip louse.

The food plants of the turnip louse are turnips, cabbage, mustard,
cauliflower, kale, rutabaga and rape.

The normal form of reproduction of the turnip louse in Texas is

‘asexual throughout the year. Observations have been made upon this

louse in Texas from Brownsville, on the 26th parallel, to Wichita Falls,
on the 34th parallel. True hibernation does not take place in Texas,
even at the northernmost point of occurrence the lice reproduce some
during the winter. The summer is the critical period in the life his-
tory of the turnip- louse, as it is forced to sheltered locations and none
of the cultivatedhost plants are grown at that time of the year. Thir-
ty-five generations of the lice were reared in pot cages in one year.

Two other species of plant l.ice are often found closely associated
with the turnip louse. These are the “garden aphis” and the cabbage
louse.

The natural factors of control of the turnip louse are widespread over
the State. Two species of parasites, Diuerevfws rarpae Curt, and Lysi-

THE TURNIP LoUsE. 7'7

phlebus tesiaceipes Cress, have been commonly found, the form.er at
College Station and the latter in other sections. Threespecies of lady
beetles have been observed to feed freely on the turnip louse. These
are flippadam-ia convergens Guer, Jegilla maculata DeG.‘ and C0001}
nella nwnda Say. Syrphid flies and lace-Wing flies are usually found
in limited numbers Where the turnip lice are abundant. A fungous
disease was very destructive to the turnip louse during the season of
19.1.4.- at College Station.

For the artificial control of the turnip louse, spraying is the most
satisfactory method. Of the materials which can be used for spray‘-
ing, laundry soap solution gives as satisfactory results as any and is
easily obtainable. The secret of success in the control of the turnip
louse is the use of the 45° elbow and an “angle” type spray nlozzle.
By the use of these it is possible to direct the spray on the under sides
of the leaves, Where the lice feed.

The preventive measures against the turnip louse are rotation, proper
planting time, trap crops, clean culture, and the destruction of the first
colonies.